Burn My Eyes by Machine Head. Nearly broke my ears when that came out... Best metal debut ever? Maybe. Also, some Fear Factory- Demanufacture or Obsolete. And Sepultura, starting with Chaos AD or Roots Bloody Roots, probably Chaos AD. If I could only ever listen to one metal band again, it'd be Sepultura.
Pitchshifter, too, especially if he's shown any interest in the dance/metal direction, ie Enter Shikari. Graduating from Shikari to Pitchshifter would be like growing up on corned beef sandwiches, then getting a steak

And Nine Inch Nails maybe? Starting with the Broken EP for the heavy stuff.
Million Dead too, and Hell is for Heroes (though NOT the second album, it's fairly rubbish) and Hundred Reasons. Well, Hundred Reasons aren't very metal, but they're incredibly good, so that might make up for it.
I'm also legally obliged to recommend the Wildhearts and Therapy? to anyone who'll listen, but tbh I'm not sure they fit the bill here. And I see everyone else has recommended Biffy.