Hey so I've always been into a good amount of harcore. Recently I got REALLY into this band called August Burns Red. I saw them last night and it was amazing. I was wondering what kind of scales/theory most bands like them use to construct their riffs and breakdowns such as in the this song. Thanks
http://www.youtube.com/watch?v=3qtk9c6ZGcM

Thats actually more like metalcore.
in answer to your question, minor key melodic riffs, and half tempo chug-chug for breakdowns. GMC has a breakdown lesson here.
PM me and ill send you some metalcore example riffs, and some good songs to learn.

Cheers
Colin

Haha that's so funny. I knew it was metalcore, but i figured if i called it metalcore than all the blues/rock people here wouldn't try to respond as it's a sub-genre. Thanks for the tip and lesson.

Reminds me of Killswitch Engage with the leads. Wicked stuff here.

yup killswitch has similar melodies. wicked's a good word to describe it haha.