It's impossible to overstate Judas Priest's importance to the evolution of metal. The band formed about a year after Black Sabbath and by the late-Seventies, they'd given the genre a makeover with a twin-guitar assault, faster tempos and a black-leather look that would forever change the way metalheads dressed."Other bands like Motörhead and Deep Purple had one guitar player and they were doing different things, more of a layering thing, but when it came to Judas Priest, they had the guitarists coming together and playing the same riff," Metallica drummer Lars Ulrich recently told Rolling Stone of their importance. "It just doubled up and gave it a heavier, bigger sound and made it thicker and more immersive."Moreover, Judas Priest helped pioneer a lot of the topics metal songs address. Their dynamic, motorcycle-riding frontman, Rob Halford, wrote frank lyrics about depression ("Beyond the Realms of Death"), fighting for your beliefs (the thrash precursor "Dissident Aggressor") and realizing there is more to the world than what what's readily apparent ("Exciter") – all before the Seventies were over. With the release of 1980's British Steel – the Number Three album on Rolling Stone's 100 Greatest Metal Albums list, which also includes their Screaming for Vengeance and Stained Class LPs – he announced himself and his bandmates as "Metal Gods," and the band brought the genre to the mainstream, scoring indelible, supercharged hits like "Breaking the Law," "Heading Out to the Highway" and "You've Got Another Thing Coming," and wowing headbangers with massive concert productions. In the early Nineties, Halford left Priest and moved in a heavier direction with his band Fight; he returned to Priest in the early 2000s and has been recording and touring with the band ever since. Because of Halford's importance to the genre, Rolling Stone reached out to him while making the 100 Greatest Metal Albums to see his personal top 10. He kindly emailed a list with a few words about each one and why it's important to him and to metal.He'll also be discussing his list today on Rolling Stone Music Now on Sirius XM's Volume channel at 1 p.m.; the show and interview will also come out later as a podcast. Until then, here are his 10 favorite metal albums.