Heck, its hard to say, I can't really say which band I like the most, but these are some that these are musicians, whose work I really value:
Insomnium - pretty young band, but it is changing metal scene with every song they create. Really, their work is fascinating, from their first demos to latest tracks from yet unreleased album. Amazing musicians, deep, poetry-like lyrics, great vocals.
Dark tranquillity - this is more emotional attachment I think, since it is one first heavier bands which got me into metal. But I really like their work, and "Damage Done" album is simply amazing piece of art.
Meshuggah - well, what can I say. Meshuggah is something you have to embrace. They have their own, quite unique sound. Combinig really heavy technical playing with interesting, uniquely melodic, even melancholic parts, not to mention intense vocals. Probably one of the most influential bands in today's metal scene.
Agalloch - pure art in its finest form. Can't really describe their work, you just have to hear it.
Nile - band that got me into death metal. Really, their songs have so much depth, I haven't seen anything like it. Lyrical theme ranging from H.P. Lovecraft books and mythos to Egyptian, Mesopotamic, Hindu etc. history, religion, customs, myths. Great guitar skills, top notch drumming.
Honorable mentions go to Death, Aeternus ("Beyond the wandering moon" is greatest blackened death album ever (imo)), Therion, Gorguts, Kataklysm.