Nearly every power metal act since the '80s has a common ancestor in Helloween. Since they formed in 1984, their sound has united classic metal's soaring heroics with thrash's brutal speed. “Future World,” from the landmark Keeper of the Seven Keys: Part I, features epic songwriting and intricate twin leads. The aptly titled “Power” is pure movement, with battle-cry melodies coiling themselves around galloping rhythms. Not to be overlooked is the band's dark humor, which helps make the 2000 rager “Mr. Torture” both furious and fun.