Power Bomb

Power Bombs are one of Samus' most powerful weapons. They must be deployed via Morph Ball mode; a few seconds after being deployed, they detonate, destroying most enemies within a surprisingly large radius. In Metroid Fusion, the blast also appears to cause a vacuum that can draw ordinary X Parasites (including ones that came from enemies killed by the blast itself) to the center of the blast. They are also capable of destroying Metroids in Super Metroid and the Prime Series.

In the Metroid series
In Metroid: Zero Mission and Super Metroid, Power Bombs are gained from Power Bomb Expansions.

In Metroid Fusion, the Galactic Federation sends Samus the Power Bombs via Data Room. Also, the SA-X used one to escape the Quarantine Bay, releasing all the X within the capsules, and thus, causing more events to occur.

In Zero Mission and Super Metroid, the Power Bombs are capable of opening Yellow Doors and breaking certain glass tubes, and in Fusion, they can destroy orange Bio-Barriers. In all three games, they are also capable of destroying Power Bomb Blocks.

In both Fusion and Zero Mission, Power Bombs are capable of revealing hidden passages and special blocks during the bomb's duration. In Super Metroid, this function is carried on to the X-Ray Scope.

In Super Metroid, Samus can perform the Crystal Flash, a technique that allows her to absorb the destructive force of the Power Bomb and convert it into energy to heal herself. She is only able to do this at critically low health levels, and it consumes a lot of her ammunition in the conversion process. She can also create Special Charge Beam Attacks using 1 Power Bomb and the Charge Beam. The Power Bomb in Metroid: Other M is arguably its most powerful appearance, capable of destroying many enemies at once, including bosses-like enemies. It plays a role in the training sequence at the beginning of the game when the Head Quarantine Officer instructs Samus to use her Power Bombs. In this game, it serves as a charged Bomb, and can be released when the 1 button is held for a set period of time. Due to its chargeable nature, it can be enhanced using the Accel Charge. Because it has unlimited ammo, it has a lengthy cooldown applied. After defeating the Brug Mass, Adam states that he has no intentions of authorizing the Power Bombs, seeing how incredible heat it dishes out, and impacting living beings which would be a "nice" way to say how instantly it vaporizes humans. Knowing how dangerous they are, they were held off for now. The Power Bombs are used extremely late within the game; during the battle with the Queen Metroid, as Samus enters her body and is continuously being drained of energy; Samus activates them on her own as her very life depends on it. Power Bombs are the only things that can "awaken" a Desbrachian, causing it to form out of its cocoon and attack Samus.

In the Prime series
In Metroid Prime and Metroid Prime 2: Echoes, the Power Bombs are arguably the strongest weapon in the game. They are able to destroy Yellow Blast Shields. It is also one of the three upgrades in Metroid Prime Pinball, where it significantly harms all enemies on one screen.

Metroid Prime
In Metroid Prime Samus had to fight the Cloaked Drone and get through a maze of electric barriers in the Phazon Mines to acquire Power Bombs; alternatively, Samus could obtain a Power Bomb Expansion in Phendrana Drifts before this by Sequence Breaking. Power Bombs can destroy objects made of Bendezium. If Samus dies while in Morph Ball form, what appears to be a Power Bomb detonates just before the game ends. This does not happen in Echoes or Corruption.

Metroid Prime 2: Echoes
In Metroid Prime 2: Echoes the Power Bomb Guardian in Dark Torvus must be defeated to acquire the Power Bombs. Samus can reach this guardian after she acquires the Spider Ball in the Sanctuary Temple. Power Bombs can destroy objects made of Denzium.

Metroid Prime Hunters
An unused model for a Power Bomb exists in the game's data, but is not found in-game.

Metroid Prime 3: Corruption
Strangely, Power Bombs are not present in Metroid Prime 3: Corruption. However, a similar, super-powerful Morph Ball upgrade, the Hyper Ball, is acquired after defeating Mogenar on Bryyo.

Super Metroid manual
"The blast of these powerful bombs can hit everything on the screen. Blocks with the Power Bomb icon can [sic] destroyed by Power Bombs."

Official Metroid Prime website
Weapon Effect: Lethal at close range.

Weapon Range: 1 - 10 m

Weapon Potential: Extreme

''The Power Bomb is Samus Aran's most powerful weapon while in Morph Ball form. The Power Bomb is much stronger than the regular Morph Ball bomb, but it does not increase the height of Samus Aran's Bomb Jump. The Power Bomb's explosion is strong enough to destroy the hardest elements, including Bendezium.''

Metroid Prime manual
"Power Bombs are super-powered bombs that will affect everything within a certain distance of their explosions. Unlike ordinary Bombs, these are limited in number, and Samus will have to replenish them herself by defeating enemies and collecting Power Bomb capsules. Some structures can only be destroyed by Power Bombs"

Metroid Prime 2: Echoes manual
"Power Bombs are super-powered bombs. Unlike ordinary Bombs, Samus will have to replenish them by defeating and collecting Power Bomb capsules. Impediment made by Denzium can only be destroyed by Power Bombs. Drop these by pressing the Y Button while in Morph Ball mode. You can find Power Bomb expansions to augment your supply, but they tend to be well hidden."

Metroid Prime 2: Echoes Samus Screen data
"The Power Bomb is the strongest Morph Ball weapon. Press Y when in Morph Ball mode to drop a Power Bomb."

Samus's Notes: "Power Bombs do not have unlimited Ammo. Use them wisely. The Power Bomb can destroy many materials, including Denzium. Each Power Bomb Expansion you find will increase the number of Power Bombs you can carry by 1."

Metroid Fusion manual
"This is the bomb in its most powerful form. Its explosion encompasses the entire screen, damaging a limited number of enemies. While in Morph Ball mode, press and hold the R Button then press the B Button."

Metroid: Zero Mission manual
"This is the most powerful form of Bomb. Power Bomb explosions are massive, encompassing and damaging everything in view. Samus has a limited supply of these Bombs. To use them, hold the R Button while in Morph Ball form and press the B Button."

Zero Mission Samus Screen data
"Set with R+B in Morph Ball form. Opens yellow hatches."

Metroid: Other M On-Screen Tutorial
POWER BOMB

Press A to change into Morph Ball mode, then press and hold 1 and release when fully charged.

Metroid: Other M manual
"Press and hold 1 until the Charge Guage is full and release to set a powerful Power Bomb."

Metroid: Other M Samus Screen data
"Effect: Damages the surrounding area. Controls: In Morph Ball mode, press and hold 1 and release when fully charged ."

Trivia

 * In Metroid Prime, when Samus dies in Morph Ball mode, a Power Bomb will activate before initiating the Game Over screen.
 * In Metroid: Other M, Power Bombs are a 'charged' bomb with cooldown, instead of ammo-based, the first game to have this feature.
 * The Power Bomb is proven to be an extremely lethal weapon as the Rhedogian, a boss enemy from Other M, is instantly vaporized if hit by a Power Bomb.
 * In both Zero Mission and Other M, the Power Bombs are acquired extremely late in the game; near the endpoint.
 * The Power Bomb appears in Dead or Alive Dimensions along with Samus, who lays one to kill Ridley at the end of every match on the Geothermal Power Plant.
 * The wrestler character King in the game Tekken 5 wields a move named Power Bomb but the move shares no similarities with the Power Bomb from the Metroid games, instead being a variant of the professional wrestling throw of the same name.
 * Paper Mario features an ability for Bombette, also called the Power Bomb, which affects all enemies on the ground.