American metal at its finest.
I'm convinced that these guys haven't been beaten, even by the mighty Megadeth or Pantera, as crowning American heavy group. They definitely have their roots in classic metal (and you can see it's still Jon Shaffer's basis for this band) like Maiden and Priest, but they've always had an element of thrash and power stylings too (more power these days, I guess).
They've gone through a buttload of vocalists, all of who had their merits I guess. Tim "Ripper" Owens (ie. the guy they made a movie about, the part-time Judas Priest cover band singer who actually got hired to replace Halford in Priest after he left) is the current one, very high vocal range and basically shrieking old-school sounding stuff. Matt Barlow, the guy before him, is my favourite, totally unique sounding, more gruff and deep like Hetfield or whatever, only less retarded and chimp-like.
Schaffer has a reputation for being an asshole, but screw it, the guy's an amazing musician, writing most of this stuff himself. His epics like "Gettysburg" and "Dante's Inferno" are complete masterpieces, and he's a complete shredder on rhythm guitar. Aside from him and the vocalist the band lineup seems to change on every record though, which sucks.