I sort of tl;dr'ed the thread since it's in the high-twenties page count, but thought I'd throw out a couple that never get mentioned.
The Canucks can rock some pretty decent metal (Annihilator - A Man Called Nothing). This is late 80s-esque, however it's shed a lot of the glam and hair. Post-Priest I'd call it. I listen to about 75% of their stuff (this being one of my favorites), but in the other 25% they fall into that metal trap so many fall into--
power polka. The bass-snare-bass-snare constant hammering of the drums that characterizes (early) Lars Ulrich and all similarly simple-minded drummers who somehow forgot how to not ruin music just because their instruments generally don't have pitches.
Sleepytime Gorilla Museum is far more progressive than metal. That said, their incredible technical expertise and amazing ability to build new instruments
(Pancreas (electric), Pedal-Action Wiggler, and my personal favorite Sledgehammer Dulcimer among those) is avant-garde in a way that surpasses pushing genre or recognizable music boundaries. The awesome duology of
A Hymn to the Morning Star and
The Donkey-Headed Adversary of Humanity really puts this band into a metal genre at their greatest. More bueno marks include that the entire band is vocally trained, the band includes Metal Violin and Metal Flute, the latter played by Nils Frykdahl, the singer whose haunting voice you hear portraying Satan in the first song, and that Dawn McCarthy (the female singer) is in another more folkish band called Faun Fables (also with Nils). She posesses an amazing pair of pipes.
And all that after I complain about it being too long to read.