I got into Tool a few years back and have been getting into heavier stuff since. I never understood the appeal of super fast playing (that's just me), but I love post rock/metal and prog metal. I don't know if anyone's mentioned these bands,or if you know them, but Opeth has some great music, and they started out as a death metal band and still incorporate it into their music which has evolved a whole lot of 20 years. Isis is amazing, very moving and beautiful and builds to a nice heavy climax. Cult of Luna is good too, some songs are very soft, but the heavy parts (to me at least) are just crushing - i love it. Mastodon's earliest stuff the heaviest, but their newest stuff is good to. There's bands like Rosetta, Russian Circles (post hard rock, not so much metal), Baroness and early Electric Wizard are some other bands that have really pushed the envelope of metal today imo. They go beyond just being heavy, and make something brand new. Hope this helps.