I'm getting a 7 string later tonight and I'm not too sure of any metal I want to play since this will be my first 7. Only metal bands I know of using 7's is Suicide Silence, Cannibal Corpse yes they use baritone 6's but 7's will work, Korn, and Whitechapel. I primarily like death/deathcore, thrash, speed, and industrial metal so there's a baseline of what I like.
Fear Factory, maybe Crossfade and Trapt (?), some Slayer is on 7 strings, earlier Meshuggah, some Deftones, In This Moment, maybe Periphery, and Trivium (especially Shogun, basically all 7 string).
Revocation's past two albums are full of awesome 7 string stuff. Trivium is a great band for 7 string licks. Currently, I'm getting into periphery and I want a 7 string so bad so i can learn their stuff! Allegaeon is completely brutal. I belive every one of their songs is on a 7 string and they even have many 8 string tunes.
Vile, Dream Theater and Spawn of Possession have all used 7-strings
Archspire uses 7s and 8s. One of them plays a 7, one plays an 8. But good fucking luck trying to learn that shit. Dir En Grey uses 7 strings on some of their stuff. The usually tune them ADADGBE. You could play most At The Gates and Carcass songs on a 7 string, at least the riffs. Solos might get weird.
Morbid Angel used 7 strings quite often. \m/