I think bands like Tool or Porcupine Tree are good entry points into the genre. Maybe not metal in a pure sense, but both are what I would consider "hard" progressive rock. Maybe not "hard" enough to be metal though.
If you feel like you're already past that point, I'd check out ISIS.
Oceanic is one of my favorite albums of all time, and the rest of their discography is super solid. Some of my other favorite metal bands are Mastodon (I like their latter stuff more), Baroness, Liturgy, Kvelertak.
