Killdozer, while not metal in any conventional sense, they had one of the most trashiest sounds ever.
Same goes for stuff by Black Flag, Disaffect, Tad, The Jesus Lizard, etc.
Anyway, if you're on a metal binge I can always list some of the most worthwile albums, 20:
Suffocation - Effigy of the Forgotten (Death Metal)
Agalloch - Pale Folklor (Folk\Doom Metal)
Arcturus - Aspera Hiems Symphonia (Avant-garde Black Metal)
Black Sabbath - Master Of Reality
Atheist - Elements (Progressive Death Metal)
Brujeria - Raza Odiada (Death\Grind)
Brutal Truth - Extreme Conditions Demand Extreme Responses (Grindcore)
Cynic - Focus (Remastered) (Progressive Death Metal)
Cryptopsy - None So Vile (Death Metal)
Fantomas - Suspended Animation (Avant-garde Metal)
Fantomas - Delirium Cordia (Avant-garde Metal)
The Melvins - Houdini
The Melvins - Stag
Fantomas Melvins Big Band - Millennium Monsterworks
Sleep - Dopesmoker (Stoner Metal)
Sleep - Jerusalem (Stoner Metal)
Coroner - Mental Vortex (Trash Metal)
Ulver - Nattens madrigal (Black Metal)
Pig Destroyer - Prowler In The Yard (Grindcore)
Ephel Duath - Pain Necessary To Know (Avant-garde Metal)