Nailgun is a struggling heavy metal band that seems to never get the break they think they deserve thanks to the endlessly bad decision making by their fearless leader, Melvin. The band is ready to call it quits when Melvin steals a magical microphone forged by Satan that grants the wishes to anyone who sings through it. By not sharing the power of the microphone with his bandmates, Nailgun accidentally triggers the apocalypse. Now Melvin must figure out a way to beat Satan at his own game in order to save the planet.