High On Fire - Stoner/Doom Metal full of crunching, pummeling riffs. Try either Death Is This Communion or De Vermis Mysteriis
King Gizzard & The Lizard Wizard - Really fuzzy indie rock mixed with psychedelia. Imagine your typical indie rock vocals being sung through a rusty muffler underneath an onslaught of fuzzy, spacey guitars. I'll be honest, I just recently picked up one of their albums and haven't had a chance to thoroughly vet it, but it seems good enough and it's weird enough that it's worth checking out. Also, they can play some mean guitars. Check out Nonagon Infinity. They have another album that just came out but I haven't listened to anything off of it yet so can't quite recommend it.
Kylesa - Sludge metal mixed with psychedelia with a female vocalist. Not like Nightwish vocals, more punk infused. Spiral Shadows and Ultraviolet are my favorite albums by them and very, very good. The nice thing is, they are fairly short and to the point, clocking in at a round 40 minutes. They just rock and get the fuck out.
Machine Head - Groove/Thrash Metal. The Blackening or Unto The Locust are both pretty good places to start. Not a big fan of their other albums to be honest but those two are good
Pallbearer - Full on m-fing doom metal. The vocalist has a bit of a smoother voice, but not operatic at all. The music is low and ponderous doom, but more melodic and with a melancholic edge. Foundations of Burden, their last album, and their newest, Heartless, are both great.
The Sword - Very Sabbath-inspired stoner metal/hard rock. Their first three albums are all good, though the first two, Age of Winters and Gods of the Earth, are a bit repetitive at times, their third, Warp Riders is great. Whatever you do, avoid their latest album, High Country. It's wimpy and fairly unmemorable.
YOB - A weird mixture of post-metal, doom, psychedlic, sludge, and stoner metal. YMMV on this one and it all comes down to how much you like the vocalist, who is like a thrash metal version of 70's Geddy Lee, ie lots of wailing and screaming. If that's not your cup of tea, well then better skip this one, but if you're intrigued, give Clearing The Path To Ascend a listen. It was one of my favorites of 2014. Atma is also a good album as well.
Vhol - If you find YOB to be to your liking, then you might enjoy Vhol as well, since the same dude handles the vocals for both bands, though Vhol is more sludge mixed with thrash metal with some killer guitar work.