Metroids are fictional alien creatures present in the Metroid universe, which give their name to the video game series of the same name.
The Metroids were created by the Chozo to exterminate the Parasites X (which appeared in Metroid Fusion) that infested the planet SR-388. Given their powers, the Space Pirates try to take possession of the creatures to use them as biological weapons, and for this reason the Galactic Federation instructs Samus Aran to eliminate the Metroids as well.
Metroids are able to attach themselves to their victims with their double jaws and suck the life energy of their prey to feed themselves, although it seems that they do not carry out a physical attack proper. In Metroid Prime, the Space Pirates carry out experiments on the Metroids living on Tallon IV, but despite various attempts at vivisection, the inner workings of the creatures are never understood.
Metroids are vulnerable to cold, so the most effective weapon against them is the Frost Ray followed by Missiles. The weaker Tallonian Metroids are vulnerable to any type of weapon. In Metroid Other M the only Metroids present are those found in the bio-weapons research center (not counting those of Sector Zero), that is a sample of Sovereign Metroid and her children. To defeat them you need to dodge the attack, fire a Frost Beam and hit them with a Super Missile.
In the other chapters of the saga there are different forms of Metroid, which will be listed later.
Newborn Metroid: They are similar to floating jellyfish, attaching themselves to the victim's head to suck their life energy. They are particularly vulnerable to the cold.
Larval Metroid: They are the best known form of Metroid and have the same characteristics as newborns, but their grip is stronger and their jaws are long. On their homeworld, SR-388, the Metroids molt and leave behind the shell of their former form as they advance to the next stage.
Metroid Alpha: After shedding for the first time, Metroids lose the ability to suck up life energy and acquire small, insect-like legs. They attack by charging and shooting fireballs or electric orbs. Their nuclear membrane shifts from top to bottom, with armor on top, The Frost Ray still affects them, but instead of freezing them completely, it only slows them down, but after molting they become more vulnerable to Samus' Missiles .
Metroid Gamma: After the second molt, Metroid Alphas become Metroid Gamma and their electric and fire powers and armor expand. Their insect-like legs become more developed and spider-like, allowing them to walk on the ground, climb and jump as well.
Metroid Zeta: On the third moult, Metroids become young adults and lose their ability to levitate, but their armor extends over their entire body except the belly, where the nuclear membrane is located, and their appearance becomes similar to that of a dinosaur. They are powerful and agile, capable of climbing walls and ceilings, and instead of firing electricity they attack by spitting flames and acid.
Metroid Omega: The fourth pack for Metroids. These adult specimens are slower than their predecessors, but are still stronger and more resilient than before, with armor surrounding their nuclear membrane. They attack with bites, tail swings, beams of fire and by throwing themselves at enemies.
Sovereign Metroid: The latest form of the Metroid, capable of producing Metroid eggs. Only a small number of Metroids have the genes to become a Sovereign from an Omega Metroid. It has a similar appearance to that of a huge crocodile with a long neck and is particularly difficult to defeat, but a Gigabomb inside can destroy it.