"'Heavy Metal"' is a song by Sammy Hagar and featured in the animated film Heavy Metal. The song was heard in the Season Twelve episode, "Major Boobage".
Background
Gerald Broflovski has a law passed outlawing cats in South Park, because of a "cheesing" drug craze among the youth. Kenny McCormick becomes addicted to "cheesing" cat urine and hallucinates as if he was in the Heavy Metal movie. In the hallucination, he is flying on a half bird/half lizard creature over a dessert and rescues a Large-Breasted Woman being tortured by mutant men with giant breasts growing all over them. He is angry when his friends catch him and lecture him about his behavior snapping him out of drug stupor.