James Hetfield and Dave Mustaine

Band: Metallica

If Metallica are the gods of '80s and '90s heavy metal, then Megadeth are like a little Cupid strumming a harp somewhere in the background. But once upon a time, Megadeth frontman Dave Mustaine was Metallica's lead guitar player, until control issues over where the band was headed got to be too much and Mustaine punched lead singer James Hetfield in the mouth during rehearsal. Mustaine was kicked out of the band, but it was a pretty metal way to go.