Metroid (species)

"Metroids are not pets. Metroids are not target practice." -Space Pirate log entry.

Metroids are a species of predators in the video game series of the same name, originating from the planet SR388. Metroids feed on the "life energy" of their prey in a manner similar to the way leeches drain a host organism's blood. However, Metroids normally drain enough energy to kill their victims, which infers that Metroids are not parasites, but in fact predators. According to the Metroid Fusion instruction manual, the Metroids were created by the Chozo to stem the spread of the X parasites. This is expanded upon in volume 4 of the official Metroid Manga. The name "Metroid" in the Chozo language means "ultimate warrior".

Physiology and morphology
The body of a Metroid consists of a thick gelatinous membrane, resembling a jellyfish, which contains a set of four red, raspberry-like, quadripartite nuclei. They have two pairs of mandibles, one for gripping their prey and the other for extracting its life energy. In early stages of their development, Metroids hover in the air. Metroid Prime 2: Echoes explains that they defy gravity by using kinetic energy that they store in their body. These larval Metroids are the ones most often encountered in the Metroid games.

Metroids are vicious predators with no natural enemies. Once attached to their prey, they are very difficult to dislodge and will otherwise drain their victim completely, killing it. They are known to finish their victims in a matter of seconds. They have an endless appetite and will feed on any and all living creatures they come across, with the exception of their own species and phazon infused creatures. This immense threat is compounded by their invulnerability to most forms of weaponry. They have only one real weakness: an extreme sensitivity to cold temperatures. Once their membrane is frozen it can be shattered by concussive weaponry (such as missiles), killing the Metroid. In Metroid Prime, they can also be killed by use of any weapon or, if you have enough energy, let them drain you until they explode.

In their natural life cycle (as seen in Metroid II: Return of Samus and the end of Metroid Fusion), Metroids gradually metamorphose to take a somewhat reptilian form eventually shedding their Gelatinous membrane completely, growing a hard organic shell, a head, and limbs. The shell removes their weakness to cold temperatures, but most forms retain a section of weak, uncovered membrane, making them vulnerable to attack. The only known forms with complete shells are the Metroid Queen and Metroid Prime. The egg-laying Metroid Queen appears to be the only form in which Metroids can normally reproduce. As they grow, Metroids also gain the ability to project bolts of static electricity and spit their toxic saliva as attacks.

In Metroid Prime 3: Corruption, it's noted by the Space Pirates that Metroids evolve differently depending on what planet they are exposed to, such as the Hunter Metroids encountered on Tallon IV (Metroid Prime). When mutated by Phazon, Metroids gain various odd qualities. (See Phazon for notes on Phazon-mutated Metroids.) Exposure to beta radiation causes them to asexually reproduce by dividing, much like a cell undergoing mitosis.

The Metroids live on a mysterious energy that they drain from their victims. What this energy is is unknown, as the victim loses no bodily fluid but perishes nonetheless. As of Metroid Prime, this energy is referred to as life energy. Metroids are stated to be energy-based organisms and increase in mass as they drain energy. Metroids can also feed off the energy used by Samus's Power Suit, which will protect Samus herself as long as it is active.

Besides draining life energy from victims, Metroids also have the ability to transfer stored life energy into another lifeform, healing it, as shown in Super Metroid. This stored energy can also be drained from the Metroid, allowing it to be used as a living power cell.

Metroid
In Metroid, Metroids were said to have been originally discovered by the Galactic Federation while researching SR388. Not long after that, the Space Pirates boarded a ship in which some Metroids were being transported and stole the specimens, taking them to their base deep within the planet Zebes. Shortly after that incident, bounty hunter Samus Aran was sent to Zebes to destroy the Space Pirates and their stolen Metroids.

Metroid Prime
In Metroid Prime, a few surviving Space Pirates found the mutagen Phazon on the planet Tallon IV and used it to rebuild their army. They exposed the Metroids to it, along with many other life-forms, including themselves. This revealed two new stages in Metroid development: 'Hunter' Metroids which had orange pigmentation and two energy-extracting tentacles and 'Fission' Metroids, which split into two smaller Metroids when attacked. These stages are presumed to be the result of Phazon mutation, as they contradict the natural life cycle seen in Metroid II, and are called Tallon Metroids in Metroid Prime 2: Echoes. Also seen in the game is a creature called Metroid Prime, which is suggested to be a Phazon mutated creature with an unknown relation to Metroids.

Metroid Prime: Hunters
Metroid Prime Hunters is the only game in the Metroid series that does not feature Metroids despite having Metroids in the demo version, Metroid Prime Hunters: First Hunt. It does, however, feature a new species: Quadtroid, a genetically engineered species that is similar in appearance and function to Metroids.

Metroid Prime 2: Echoes
In Metroid Prime 2: Echoes, the Space Pirates bring Metroids with them to Aether. Metroids in this game appeared with red membranes. The Ing later possessed some Metroids, creating Dark Metroids. Also seen are Metroid cocoons, which release very small infant Metroids which need to come in contact with Phazon in order to grow to the size of normal Metroids. Very young infant Metroids cannot yet absorb energy, and instead use ramming attacks to damage their foes. The logbook scan for these infant Metroids suggests that the Space Pirates may have somehow created this Metroid strain to be less dangerous and easier to transport, supported by the fact that in the end of Metroid II: Return of Samus, the Metroid hatchling already is in it's most common (larva) form when it hatches, as Samus approaches it.

Metroid Prime 3: Corruption
In Metroid Prime 3: Corruption, four new Metroids are introduced. These Metroids are the Miniroid, the Phazon Metroid, the Hopping Metroid and the Metroid Hatcher.

Interesting to note, in a room on the Space Pirate Homeworld in Metroid Prime 3: Corruption, there are three empty tanks. When scanned, the first reveals that the Metroid sample taken from Zebes has proven highly aggressive, even for a Metroid. The second tank reveals that a particular strain of Metroid from Tallon IV has been moved for further examination. The final tank reveals that the SR388 Metroid has incredible DNA altering abilities and is being taken to a Research Station to be studied. Obviously, the SR388 Metroids will be purged in Metroid: II, the Tallon IV Metroids were the normal but weaker green or red Metroids along with Fission Metroids from Metroid Prime, and Zebes was the planet where the Metroids were originally moved to in Metroid (game)/Zero Mission by Pirates and would be returned to in Super Metroid.

Metroid II: Return of Samus
In Metroid II: Return of Samus, seeing the dangers the Metroids posed to the galaxy, the Galactic Federation attempted to destroy them. After two failed attempts by the Federation's army to eradicate the Metroids on their home planet of SR388, they called on Samus Aran to deal with them, as she had previously been the only person able to survive several encounters with the creatures. It was in this game that the natural Metroid life-cycle was revealed.

The game begins with a total global Metroid population of 39. Samus's goal was to explore SR388 and hunt the Metroids down one by one. As she progresses further into the planet, the Metroids continue to evolve further into their life-cycle, eventually culminating into the Omega Metroids. Samus eventually makes her way into the Metroid nest at the center of the planet, destroying several Metroids before engaging in a final battle with the Metroid Queen.

After the Queen was destroyed, an infant Metroid hatched and imprinted Samus as its mother. Because of Samus's efforts, this infant was the last surviving Metroid in the galaxy. It helped Samus escape from SR388, and she took it back to the Federation Academy.

Super Metroid
In Super Metroid the Metroid larva that had imprinted on Samus was studied by scientists, and it was found that the Metroids' potential as life saving creatures was as great as their destructive powers. Right after Samus left Ceres Station, the Space Pirates besieged it and Ridley stole the Metroid larva, taking it back to the Space Pirates' rebuilt base on Zebes.

The Space Pirates quickly used beta rays to multiply the Metroid into a new army of feral larval Metroids. In Maridia Samus also finds many Space Pirate attempts of clones of the Metroids called Mochtroids. While they could leech life, they were weak and could not latch onto their prey. At the end of the game, the Metroid larva sacrificed itself to save Samus. Before dying, the Metroid was able to give an example of its life saving properties that could benefit all civilizations (what the scientists revealed at the beginning the game): transfering energy to living beings instead of simply absorbing it. Its demise caused the Metroid species to become apparently extinct (and showing they have the capacity for compassion at the same time). Worthy of noting is the fact that the Larval Metroid was able to grow into a tremendous size without molting to its next stage of a Metroid's natural life-cycle (it's actually bigger than a Metroid Queen). It could be that prolonged exposure to beta-rays made it grow unnaturally; another possibility is that the Metroid, not being in its natural environnement (thus missing some sort of compound/chemical only present in SR-388), was restricted to the larval stage.

Metroid Fusion
Metroid Fusion takes place shortly after Super Metroid and is considered "Metroid IV" (in part due to its tentative title) on the timeline. On planet SR388, the Metroids had been the top predators, and with them gone the ecosystem was thrown completely out of balance. Samus was hired to protect some Federation scientists who were studying the recovery of the SR388 ecosystem. While they were on the planet, Samus was infected with an X Parasite. She was rushed back to Federation Headquarters with a minimal chance of survival. It had recently been discovered that the Chozo had created the Metroids to prey upon the X Parasites, which were dominating the ecosystem of SR388. Using this information, the Federation saved Samus by injecting her with a Metroid vaccine made from a DNA sample of the deceased hatchling.

Later in Metroid Fusion, it was revealed that the Federation had a secret Metroid breeding program going on (see Restricted Lab), presumably based on clones of the last Metroid. The program was destroyed by a powerful X Parasite mimic of Samus, the SA-X. The entire section was detached from the station and ejected into space, just after Samus escaped, completely destroying the Federation's research. However, one Metroid had escaped and advanced to Omega level, and Samus had to defeat it before evacuating. At this point, the only known Metroid DNA resides within Samus Aran.

Appearances in other Media

 * Metroids, or a very similar creature, appeared in another Nintendo game, Kid Icarus (and the sequel, Kid Icarus: Of Myths and Monsters), under the name of Komayto, stated in the instruction manual to have come from another planet. This creature can be found flying around Skyworld in packs. Kid Icarus was created on the Metroid game engine.


 * A Metroid is a collectable treasure in Wario Land 2. They are also often in 9-Volt's microgames in the WarioWare series, such as Touched and Twisted.


 * Metroids made an appearance in Kirby's Dream Land 3 for the SNES. If Kirby freezes all the Metroids in the level, Samus removes her helmet and gives Kirby a Heart Star.


 * Metroids make an appearance in Super Smash Bros. Melee as a trophy as well as Infant Metroid being seen in the opening cutscene, and make another appearance in Super Smash Bros. Brawl as an Assist Trophy, with the ability to latch onto opponents and drain them of energy.


 * A Metroid is a furniture item in Animal Crossing: Wild World for the Nintendo DS. It resembles the Infant Metroid in a large capsule. The piece plays the Super Metroid title theme song when tapped. This will also be in Animal Crossing: City Folk, due to compatibility with the previous game's items.


 * Metroids must be removed from Samus's head in a microgame on WarioWare: Touched.


 * Metroids wander onto stages randomly in Metroid Prime Pinball and also have their own minigame, Metroid Mania.