Colossus is a very strong mutant who can change from a normal-looking human form into a form with metallic-like skin. He is a member of the X-Men.
Piotr Rasputin grew up on his family's farm in Russia and lived there until he was recruited by a group of European mutants seeking to establish a society in which mutants and humans could peacefully coexist. Colossus, as he came to be called, was uncomfortable with the violent tendencies of the group and their willingness to use whatever means necessary. This uneasiness led him to help the X-Men to defeat the terrorists.
Since joining the X-Men, Colossus has been shown being trained in martial arts by X-Men leader Cyclops.
Colossus proved to be the most formidable phsyical obstacle to the powerful alien Tyros when he attacked the X-Men Mansion.