I am going to try to organize all my metalcore related recommendations in this one post.
Bleeding Through - Symphonic Metal (new material), Metalcore
Their new album Declaration should be a part of any metal fans collection. It was produced by Devin Townsend, and features some of their greatest material. They dropped a lot of their hardcore roots in favor for a more symphonic metal sound, kind of like a metalcore version of Dimmu Borgir. If you need one song to convince you to get the album, listen to Sister Charlatan, one of the most epic metal songs to date.
Botch - Mathcore, Metalcore
Their album We Are the Romans is known as one of the greatest works in mathcore. It leans more towards the hardcore side of things, but still keeps a great deal of complexity. It keeps the spirit of hardcore and punk with the musical depth of math rock, and the end result is a terrific album.
Converge - Metalcore, Hardcore Punk
One of the lead driving forces of the genre, this band has released one of the most impressive series of albums ever. Jane Doe is widely considered one of the greatest albums in the field of metal. The album is one of the most emotional albums I have heard. Their newest effort Axe to Fall is probably their most accessible. It is probably their most metal album, and contains some progressive influences.
Yakuza (Avant Garde, Metalcore, Punk Jazz)
This band is fucking crazy. They take metalcore and mix it with elements of jazz and world music. They have songs ranging from 2 minute hardcore punk outbursts to 40 minute jazz tunes. They are inspired by acts like King Crimson, John Coltrane, and have shared the stage with familliar bands like Opeth, Mastodon and The Dillinger Escape Plan.