All of the above are good. Maybe also give Oh, Sleeper's new album a go, maybe closer to post-hardcore but you'll probably like it.
I'll try not to repeat what others said. Atreyu August Burns Red Bury Your Dead Dance Gavin Dance A Day to Remember Five Finger Death Punch From Autumn to Ashes In Fear and Faith Lamb of God Light This City Mastodon Parkway Drive Phoenix Mourning Shadows Fall Slipknot Soulfly Suicide Silence That's a good mix of hard rock/metal/metalcore/screamo bands. Some are straight up screamo while others have some melodies and that kind of thing in there.
They aren't metalcore either. There is nothing hardcore about them, its all metal. They're just very heavy, somewhat progressive (on soundtrack to your escape anyway), alternative metal.
Most metalcore bands don't have much hardcore about them, anyway, but yeah they're pretty much just alternative metal nowadays and Jacob would probably like them anyway.
I'm just listing off stuff that is a mix of hardcore, metal, metalcore that I think Jacob would like, mostly the more melodic songs. He basically sounds like me but 4 years ago.
Ok cool. I went to my uncles show yesterday and this band called Vanna was excellent..they are along these lines to
You guys just forget 1 little band: Silent Civilian - Rebirth of the Temple IMO the best metalcore band out there (and I know all the others posted here)