I would also recommend Mastodon, especially their newer stuff. Crack the Skye was released this year, they're touring with Metallica, and the singer reminds me a bit of Ozzy, especially on the first track, Oblivion.

Also check out Badmotorfinger and Superunkown by Soundgarden. Even when in 4/4, Matt Cameron, their drummer, does a great job of keeping the rhythms electric.