Clutch may sound familiar to you because they (as well as GWAR, and a few other bands) were on an episode of MTV show Viva La Bam. They played on top of the hill during the downhill "sled" race. The singer has provided guest tracks on a few songs, one in particular stands out. :-D
He provides vocals for the last verse, he's not the clown in the video, though.
I think that I may have listened to Clutch's album Robot Hive/Exodus more than any other album I own. There is simply nothing bad I could ever say about that album. Any time I mention that album around any of my friends (I burned them all copies, I was 14, sue me.) at least one of them pipes up "That was like the best album ever, dude." The guitars are beautiful and melodic, the drums are steady and pounding, and the vocals impeccably crystal clear and wonderful. The album weaves symbolism with allusions to classic rock, I can think of references to Rush, REO Speedwagon, Kansas, and Boston without even thinking about it. The album also references various mythologies, including the mythos of H.P. Lovecraft. I cannot say enough good things about this album.
That said, I've been kind of disappointed with their two newest albums, From Beale Street To Oblivion (2007), and Strange Cousins From The West (2009) but I think that might just be because I'm holding them up to Robot Hive/Exodus for comparison, and quite simply nothing compares. It just couldn't. Ever. They're not bad albums by any means, just disappointing.
So, I'll leave you with what many believe to be the strongest track on Robot Hive/Exodus, which you might recognize if you played the Xbox 360 game PREY. (Though I hope for your sake you didn't.)