

series is the Metroid larva, although other forms have made appearances in the series. The form most commonly depicted in the Super Smash Bros. They can also phase through platforms, similar to Phazon Metroids in Metroid Prime 3: Corruption. In their Smash appearance, Metroids act the same as they do in the Metroid series, grabbing players and dealing damage. Because of her Metroid-fused DNA, Samus herself is the last remnant of the Metroids, having become the "ultimate warrior" of the Chozo. Upon this discovery, she set the ship on a collision course to SR388 and escaped, destroying the last remaining Metroids upon impact. During her mission at the infested Biologic Space Labs Research Station, she discovered that the Galactic Federation had begun a Metroid breeding program. This procedure infused her with Metroid DNA, giving her characteristics such as immunity to X Parasites and a weakness to cold temperatures. After being infected by an X Parasite, the Federation saved her life by injecting her with the Vaccine "Metroid", which was created using the hatchling's DNA. However, Samus's actions caused the Metroids' natural prey, the X Parasites, to multiply and thrive once more.

After his retreat to the Space Pirate base on Zebes, the hatchling was eventually killed by Mother Brain, seemingly leading to the species' total extinction. She returned this specimen to the Ceres Space Colony for research, where it was subsequently stolen by Ridley. Samus was eventually commissioned by the Galactic Federation to travel to SR388 and put them into extinction, although she spared a single hatchling that imprinted on her. They introduced Metroids as invasive species to other planets, such as Zebes and Tallon IV. However, the Metroids' parasitic nature makes them a constant target for Samus's archenemies, the Space Pirates. The word "Metroid" means "ultimate warrior" in the in-universe Chozo language (the real-life etymology of the word is a portmanteau of "metro" and "android" ).

Metroids were created by the Chozo to prey on the X Parasites, and became native to the planet SR388. Metroids are also known for their ability to adapt and grow in any environment while most Metroids are seen as their jellyfish-like larval form, they become larger and more bestial as they develop, culminating in the draconian Queen Metroid. If one grabs onto her, the only way for Samus to shake it off is to drop a bomb while in her Morph Ball form, which deals damage and detaches it from her. They are resistant to most forms of standard weaponry, but are exceptionally weak to cold temperatures, so Samus can destroy them with her Ice Beam or Ice Missiles. The creatures are a parasitic species that use their gigantic teeth to drain energy from their prey. Metroids first appeared in Metroid as an enemy that played a crucial part in the game's storyline, and have appeared in every Metroid game since, with the exceptions of Metroid Prime Hunters and Metroid Dread. Official artwork of a Metroid from Metroid II: Return of Samus, which was the basis of the Melee trophy design.
