This looks like an old question, it's doubtful you'll be coming back to check on it after all this time. Still, I'd like to put in my two cents just in case.
I noticed a few people listed old progressive or "proto-metal" bands like King Crimson and Blue Cheer. These bands can certainly be pretty psychedelic, but that's probably not the idea of "metal" you were going for.
Try the more recent stoner or desert rock movements. These and a few other scenes featuring heavy riffs with trippy lyrics and sound effects emerged in the 90's and still run pretty strong today, if mostly unnoticed by the general public.
To name a few, check out:
Also look into the bands Witchcraft and Graveyard. While not as heavy as some of the others I listed, these two groups from Sweden are definitely psychedelic. Especially Graveyard's first album.
Finally, check out the website Music Roamer. If you like any of these suggestions, type their name into the search box and it will bring up a web of related artists. Double click on one of those, and it expands the web to show more like that one.