Brutal death metal has always stood out to me as the heaviest overall genre. I know people like to point to black metal because of the subject matter and theatrics, but it has always lacked the musicianship and overall accessibility for most metal heads. To me, it's merely a hyperbolic derivative of metal, and not in a good way.

Cannibal Corpse was a great pick, as is Deicide and Morbid Angel. Death's instrumentation could put them in contention but Shuldiner's vocals were too high-pitched when compared to his contemporaries. It works well for the band, but it's just a notch beneath the brutal death bands in terms of aggression.

Personally, Lamb of God's Ashes of the Wake was just on another level at the time of its release. However, the subsequent album, Sacrament , seemed to take a step back in terms of overall heaviness. Consequently, they seem to get unfairly dismissed by fans. Randy Blythe's vocals are harsh 100% of the time, unlike most metalcore or melodic death bands. Plus, Adler's double-bass drumming is just a work of art.

I will also submit Meshuggah in any argument involving heaviness. I know most people like to shite on djent as a genre, but these Swedes are the real deal. Chaosphere may not be as impressive as Nothing in terms of virtuosity, but it can easily be viewed as the band's most brutal album from start to finish. Plus, they're one of the most intelligent bands performing today along with Gojira.

I've never cared for bands like Electric Wizard and other doom metal acts because it just puts me to sleep after awhile. Don't get me wrong, I love Candlemass, Crowbar, Down, and Black Sabbath's Master of Reality, but I can only handle so much. While tuning down is an essential aspect of heaviness and metal in general, it isn't the end all be all in determining a band's "weight". I've always preferred the speed and furious pacing of thrash and death because it seems much more frantic and chaotic.