There have been a lot of great classic albums mentioned here, so I felt that I should maybe add in some current great metal albums, to show that YES, the classics rule, but there is some good stuff being put out still nowadays.
1. Arch Enemy - Rise of the Tyrant; not everyone will like the death/blackmetal vocals, but the music and playing is superb.
2. Trivium - Shogun - truly one of the best metal albums last year; somewhat screamy vocals though and Trivium suffers from a bad teenie image (just like Bullet For My Valentine).
3. Def Leppard - Songs from the Sparkle Lounge - I love this one
4. Black Stone Cherry - Folklore and Superstition. Makes you want to crack out the bourbon and sit on the front porch (or shoot small animals in the backyard with your shotgun, ok not in the UK though).
5. Megadeth - United Abominations. It's not as great as the classics, but it does remind you why you should still keep an eye on this band.
6. Lordi - largely overlooked, Kiss on Steroids. Deadache or The Arockaplypse are both kickass albums.