Sequence Breaking

A Sequence Break is an act that breaks the standard sequence of events in a game ("taking another way through the game than a player is likely to use on the first play-through"). This may amount to collecting an item earlier than intended or skipping a segment entirely. Sequence breaks often rely on glitches, but sometimes creative thinking is enough. Efficient sequence breaking is the key to many time improvements in speedrunning. For example, in Metroid: Zero Mission, it is possible to kill Ridley before killing Kraid, and also to obtain the Varia Suit before the Ice Beam.

Sequence breaks are ubiquitous in the Metroid games. In fact, many sequence breaks seem to have been known to the developers. For instance, the secret Wall Jumping and Bomb Jumping techniques in Super Metroid directly lead to several sequence breaks, but the latter lacks practical use otherwise. Further, it is nearly impossible to get stuck or cause crashes in Super Metroid when entering areas without the supposedly required equipment, indicating that the designers were aware of the possibility that players would do so.

Most re-releases of games, most notably in the Metroid Prime Trilogy, correct speedrunning techniques to prevent sequence breaks from occurring.

Main series
Note: this article also lists unintended techniques that do not have any discovered use to break a sequence.

Metroid

 * A "Bomb Boost Jump" can be performed by laying a bomb and unmorphing before it detonates. Samus will be sent into the air by the bomb, and she can jump higher than normal.
 * If Samus rolls off a ledge in Morph Ball form and unmorphs, she will be in her standing sprite, and she is able to jump. This is similar to the Jump Boots, and can also be performed in Metroid II: Return of Samus.
 * With this technique, it is possible to reach Kraid in his lair through one of the two possible paths without freezing a Ripper.
 * The Varia Suit can be collected without the Ice Beam by Door Jumping up to the Varia Suit's room in the shaft that is two rooms from the Varia's location.
 * The Varia can also be collected without the High Jump Boots but with the Ice Beam. Samus must abuse a Waver by freezing it over and over to get to the Varia. The Waver may not always line up correctly, and if this is the case, Samus should use the Ice Beam-less method.
 * Ridley's Lair and the area leading to the High Jump Boots can be reached without the Bombs by using the Door Jump in the "green bubble" section of Norfair.
 * The Ice Beam can be collected without the Bombs by using the Door Jump.
 * Kraid and Ridley do not have to be defeated to get into Tourian. If Samus lures a Reo from Corridor Number Two into the room with the Stone Statues and freezes it above the acid, she can perform a difficult Bomb Jump to reach the other ledge.

Metroid II: Return of Samus

 * As stated above, Samus can roll off a ledge in Morph Ball form and unmorph, and then jump in midair, as in Metroid.
 * If Samus jumps into an enemy, she will be knocked back, and can jump higher than normal in the air. This has particular use when she is trying to climb a wall of Autracks. Further, if Samus is damaged while she is in midair, the game will allow the player to jump again off nothing.
 * Though it does not seem to be the case, Samus can make an indefinite Bomb Jump. She must lay a Bomb, and before it explodes, lay another one, and so forth.
 * If Samus has sufficient Energy Tanks, she can go through the purple liquid without having to drain it by defeating all Metroids in an area. Thus, this can be used to move to new areas without having to kill any resident Metroids.
 * This does not work between the final areas Phase 8 and Phase 9 as there is instead a spiked structure sealing the latter off until all 3 remaining Omega Metroids are defeated.
 * Samus can rapidly fire her weapons when in an enemy-filled room to slow their movement down.

Super Metroid



 * It is possible to skip the first Torizo via Arm pumping.
 * A glitch commonly known as the "Green Gate Glitch" involves a Shutter with a green light that is on the left of the machine. Samus must jump and fire in a certain area of the Shutter to make it lift from the wrong side.
 * Samus can jump higher and farther underwater, or under Lava if she turns off the Gravity Suit immediately after jumping. This technique is known commonly by the speedrunning community as the "Gravity Jump."
 * The Mockball allows for Early Super Missiles or the Ice Beam.
 * The Energy Tank in the blue part of Brinstar can be reached by using a "Damage Jump".
 * By using a quick Speed Booster charge, Samus can collect the Energy Tank in the pink portion of Brinstar much earlier and without the Gravity Suit.
 * The Wall Jump can be used to collect Power Bombs before the Grapple Beam, the Wave Beam, Spazer Beam, X-Ray Scope, reach Kraid early, and get into the Wrecked Ship without the Grapple and thus collect an early Gravity Suit.
 * Getting to Draygon without the Grapple Beam via getting the Gravity Suit early (see above) and the wall-jumping technique.
 * The Speed Booster, High Jump Boots and Power Bombs can be collected later than usual if other sequence breaks are performed, although the High Jump can also be skipped altogether.
 * The Speed Booster can also be skipped altogether by using the Ice Beam to freeze a Puyo or a Mochtroid to clip through a Pit Block in the room before Botwoon, causing them to crumble, and allowing Samus to skip the Speed Booster Blocks normally needed to reach the rooms.
 * The Baby Metroid can be avoided in Tourian through dodging with the Space Jump, or with the usage of a Shinespark.

Metroid Fusion

 * Using quick manuevers, Wall Jumps and Shinesparks, numerous Energy, Missile and Power Bomb Tanks can be obtained without the otherwise required equipment.
 * There is a secret conversation that can be seen by using a series of tricky Shinesparks in Sector 4. This almost allows the player to skip the Diffusion Missiles; the developers thought to lock the door to the Main Deck. It is also possible to access this secret conversation through the use of a difficult, pixel perfect ice missile in the room before the diffusion missile data room shot in a downward-diagonal direction to freeze one of the Powamps before they puff up and block Samus's path. This method was fixed in European releases, however.
 * It is also possible to fight Nettori and Yakuza early by performing bomb and wall jumps in succession.

Metroid: Zero Mission

 * The Screw Attack can be acquired early. First, Samus must take a secret route in the main 'bubble shaft' of Norfair. A well-executed Bomb Jump or Wall Jumping and destruction of Missile Blocks will bring Samus to the Screw Attack.
 * The Varia Suit can be collected by freezing Wavers, or by using several Bomb Jumps to reach the Varia's room. This also means it can be collected without the Power Grip.
 * The secret Missile Tank in the first long shaft of Brinstar can be collected using Wall Jumps and Bombs.
 * The Super Missile Tank near the Brinstar shaft can be reached using several Ballsparks. That in the Chozo Ruins portion of Crateria can also be reached with several Wall Jumps and Shinesparks as well.
 * As in Metroid, the Long Beam can be skipped by taking an alternate route of Fake Blocks. Skipping the Long Beam forces Samus to use Missiles in order to hit objects at long range.
 * The Wave Beam can be collected early via skipping the Ice Beam.
 * The Imago can be skipped by taking an alternate route to Ridley's Lair, or by getting early Super Missiles (above).
 * It is possible to completely skip the Varia Suit, but when the Ruins Test is completed and Samus collects the fully powered suit, which activates the three Unknown Items revealed to be the Gravity Suit, Space Jump, and Plasma Beam, Samus gains the Varia Suit anyway as the new suit provides it.
 * It is possible to enter Tourian without obtaining the Ice Beam. If she goes into a room with Metroids in it, however, she will be trapped with no way to kill them.
 * It is possible to defeat Mother Brain and exit Tourian without the Speed Booster, by wall jumping or bomb jumping up the wall near the west entrance to the ship.
 * It is possible to obtain early Super Missiles without the Ice Beam by entering a secret route to the lower areas of Norfair. However, this makes the fight with Kiru Giru much more difficult, as it now requires the use of Wall Jumps to attack the Tangle Vine.

Metroid: Other M

 * An Energy Tank can be obtained earlier than usual in an area that would normally require the Speed Booster to reach in the Cryosphere by utilizing a break in an overhead Morph Ball passage and repeatedly interrupting Samus's spin jump by shooting.

Metroid: Samus Returns

 * The first two puzzles on the Surface with steep vertical shafts and on-screen notifications explaining how to use the Missiles, Free Aim and Power Grip can both be skipped by Wall Jumping. **However, doing this with the first requires much more precision than the second.
 * In Area 2, it is possible to skip the Spring Ball puzzle by deploying a bomb as close to the fans as possible without it getting absorbed by them. Then, she must also stay as far away from them as possible in Morph Ball mode in order for the impact to send the Ball flying diagonally and very briefly above the fans, making it possible Samus to place another bomb above them and break the Bomb Blocks, allowing her to proceed without acquiring the upgrade from Arachnus, and thus skip its battle completely.
 * In the same area, it is also possible to skip the High Jump Boots puzzle by jumping above the fan and at the highest point, quickly going into Morph Ball mode and placing a bomb over the aforementioned fan. Then, Samus can repeat the first two steps in the previous manuever and use the bomb placed during the previous jump to gain additional height, un-morph, grab onto the ledge, and reach the top without the High Jump.
 * Like in Metroid Fusion, there are several expansions that can be obtained early through various unintended manuevers.

Metroid Prime
Note: Some of these glitches present in the North American GameCube version have been fixed in later versions, including Japanese New Play Control! and Metroid Prime Trilogy versions for the Wii.
 * Using the Scan Dash glitch allows for the Space Jump Boots to be acquired before any other upgrades. The Scan Dash was removed in later versions of Prime, so Samus must perform an alternate, but difficult method by locking on to one of the Seedlings in the Temple Hall and heading backwards to the Gunship in Landing Site, before doing the rest like the NTSC version.
 * Samus can get into the Furnace room without the Spider Ball by using a clipping glitch, or a Ghetto Jump. When she reaches the Hall of the Elders, she can jump on a Radiation collector to reach the room's Bomb Slot, and then practice several other jumps to get to the Reflecting Pool. Once there, she can simply stand on a Stone Toad and reach the Antechamber and Ice Beam early. This is usually performed before encountering Flaahgra.
 * In the Japanese New Play Control! version, it is possible to do this in the Furnace using a Spring Bomb Jump. In the Trilogy version, however, an invisible wall was added to the upper entrance of Furnace's Morph Ball tunnel until Samus collects the Spider Ball.
 * When standing on a Stone Toad in both New Play Control! and Trilogy versions, Samus temporarily loses her ability to jump.
 * The Plasma Beam can be reached without the Spider Ball by either successfully performing two jumps in the Twin Fires Tunnel, or by exploiting the scan dash glitch on the Spider Ball Track in the room. Then in the Geothermal Core, several jumps can be exploited to reach Plasma Processing.
 * The Power Bomb Expansion in Security Cave can be reached using several difficult jumps. This will give Samus early Power Bombs and also enable early access to the Artifact of Spirit and other such items. Notably, this trick can be performed in the Metroid Prime Trilogy version of the game, despite the changes made to jumping.
 * The Power Bomb Expansion in the Magma Pool can also be obtained early by using the infinite speed glitch. In the GameCube version, this requires the Boost Ball.
 * Early Morph Ball via Space Jump.
 * Early Gravity Suit via part of the "Early Plasma Beam" (namely passing the Twin Fires Tunnel without the Spider Ball.)
 * The Hive Mecha can be skipped via an L-Lock Spring Space Jump. This allows for Missiles to be acquired without having a battle. Alternatively, a scan dash can also be used to escape the Hive Totem, and if Samus returns, the Hive Mecha is gone, replaced by the Missile Launcher.
 * The Missile Expansion in Main Plaza's half-pipe can be reached using a Ghetto Jump, as another means of early Missiles.
 * The Gravity Suit and crashed Frigate Orpheon can be skipped via Bomb Jumping over the bars in Great Tree Hall.

Metroid Prime 2: Echoes
Note: Most of these glitches present in the GameCube version of Echoes have been fixed in the Japanese New Play Control! and Trilogy versions for the Wii.
 * Using the infinite boost glitch, Samus can avoid losing the starting items that would normally be stolen by the Ing. However, if Samus gains several items and then re-enters the room where she first sees Dark Samus, she will not only lose the items stated she lost, but also any upgrades (i.e., Dark Suit, Light Beam, etc.) she acquires. Also, although Samus appears to have the Grapple Beam and Power Bombs stolen, she does not have them at the start of the game. This also lets the player gain access to Torvus through the Half-Pipe located in the Agon.
 * A much faster (though somewhat harder) option is to jump onto the monitors in the room and jump out of bounds, then navigate around the item-loss area. This is possible in all versions of the game [GameCube, Trilogy].
 * Using a carefully executed Bomb Jump and Screw Attack, Samus is able to completely bypass getting the keys to the Hive Temple.
 * Early Power Bombs via a series of difficult jumps in the Temple Grounds. When used on bosses not designed for it, the effects can range from a one-hit kill (Boost Guardian) to no effect at all (Amorbis)
 * By Ghetto Jumping in the Abandoned Base, the player can enter the Torvus Bog and clear most of the game without the Dark Suit. This can still be performed in the Metroid Prime Trilogy.
 * In Watch Station Access, on the side connecting to the Main Gyro Chamber, the player can reach the other side of the room without the Grapple Beam by morphing off of the platform and subsequently unmorphing while Samus is blocked by the platform, then space jumping to the other half of the pit. This will confuse the game and respawn Samus on the far side of the pit, allowing her to get the Energy Tank early, and if combined with the trick below, can let the player acquire the Screw Attack without the Grapple Beam.
 * An incredibly difficult trick involving scan dashing can be performed in the Grand Abyss. By locking on to one of the drones on the right side of the room, the player can scan dash to land on top of one of the other drones on the left side of the room, which will carry Samus across the room and allow her to skip using the portals. When she enters the Vault, she can scan dash again onto the right platform with a spinner and continue to obtain the Screw Attack without entering the Dark World, and if the Grapple Beam is not acquired at this point, it will be skipped entirely.
 * Note that if the player fails to make the scan jump onto the drone on the first try, the game must be reset, as the drone will never stop moving and the trick will become impossible.
 * Alternately, a wallcrawl can be used to obtain the Screw Attack, though this is much slower.

Metroid Prime Hunters

 * Samus can reach the end of the Piston Cave (and skip the entire sections of it) by unmorphing at the Morph Ball tunnel in the Processor Core and performing "Missile Pushes" to blast herself into the tunnel.
 * The battle with the Barbed War Wasps in the Ice Hive can be skipped via Missile Jumping to reach the ledge where the Missile Expansion is located.

Metroid Prime 3: Corruption
Note: Most of these glitches have been fixed in the Trilogy re-release of Corruption.
 * Early Spider Ball via series of glitches.
 * Early Hazard Shield via early Spider Ball; this leads to an endgame.