Shai Hulud, they basically invented the genre. Uh. Well, after Shai Hulud you'll probably feel let down by a lot of other metalcore.If you're listening to converge and botch and you want to make it mathier (is that a word? now it is) there's Coalesce. They recently released Ox, a really great album. I could recommend a range of shitty metalcore as well, because I like it, but I doubt you would.
I'm not really sure how Coalesce are mathier than Botch, they definitely aren't on the albums pre-split. Coalesce are the plodding, Led Zeppelin obsessed ones. And saying Shai Hulud invented metalcore is more than a bit misleading since they apparently formed in the mid-'90s which means Integrity, Earth Crisis, Rorschach and Converge all predate Shai Hulud by about 5 or 6 years and quite a lot of other bands were already active or forming at the same time.
Sean, get yourself some old Integrity, like Humanity Is The Devil. Forget Earth Crisis, a few fun songs but you can comfortably skip them. Chokehold are absolutely essential, you
need Content With Dying but be warned, it's really sloppy and rough edged. Totally worth it though. Deadguy are a good idea too, get hold of Fixation On A Coworker. Oh, and Rorschach, this is very important. Basically, after Void went shit and split the intensity level dropped significantly in hardcore. We had to wait until Rorschach for things to get fucked up again. Get Autopsy, that's the discog. Finishes on the best cover of My War you'll ever hear. You're also going to need The Swarm aka Knee Deep In The Dead's brilliant Parasitic Skies. You know Cursed right? Well before Cursed there was The Swarm, and they make Cursed sound like a damn pop-punk band. Fucking Invincible At One A.M. is downright fucking feral and will eat your face for not being nailed thoroughly enough to the X. Unbroken aren't strictly metalcore but they're very important to the whole thing, and besides, it's fucking Unbroken so you need it. From the UK check Canvas for the weird shit, Thirty Seconds Until Armageddon for Drone and Lost being two of the best mosh songs ever and Stand for being excessively reasonable but with awesome riffs. I say fuck Slavearc, hardline bollocks, and XCanaanX were dogshit too no matter what anyone says.
Oh, and are you already up on the whole kinda screamo/metalcore/crust type thing from Bremen? Because if not,
dude. Acme, Mörser, Systral, Carol, Acheborn... Awesome bands. Oh, and we need to talk about Belgium. Metalcore is one of the only genres in existence where Belgium is a big deal. You're going to need a bit of early Congress and Liar, and fuck it, Arkangel. Yeah it's basically one riff all the way through Dead Man Walking but y'know, the chug is good and they're named after an animal liberation magazine so who cares.
So remember these things: Germans and Canadians outbr00dal most people and are more interested in politics than the edge, the British are weird, Belgians are all militant vegan edge and call their labels things like Sober Mind and Good Life and the Americans are somewhere in the middle of it all.