[Jomb]

Metal is not my primary genre anymore, hasn't been in over a decade...

If your question was just psychedelic music in general I'd have a list longer than my arm.

But for bands which are generally considered to be metal, of the ones I've heard, Cathedral is the trippiest. I actually like Lee Dorian's vocals to. That and the huge massive hypnotic guitar riffs and the hallucinatory lyrics with their other-wordly imagery.

There is some question of what the word "psychedelic" means in terms of music though, it can mean different things to different people.