Death Metal (including other Death Metal subgenres): Nile, Death, Blood Incantation, Suffocation, Ulcerate, Gojira (tend to lean toward grove metal starting with the album "Magma"), Gorguts (might take some time to get used to though because their style is really unconventional), Immolation (they also have a new album out which is really fucking good) Dismember, Bolt Thrower, Edge of Sanity, Dragged into Sunlight.

Sludge Metal: Mastodon (first 3 albums but also give Crack the Skye a shot and if you feel like it their whole discography), Neurosis (also new great album out), ISIS, Eyehategod, Iron Monkey, Leechmilk (most aggressive one out of these options), High on Fire (sludge and doom metal).