A subgenre of doom metal and drone metal, which is even more inaccessible and minimalistic than funeral doom. The sound is very slow, sometimes being as slow as 10 beats a minute, and very heavy, with deafening, downtuned guitars. There is extremely minimal drumming, and little singing. If there is singing, it is usually done in a shrieking manner, similar to that of black metal. Drone doom is meant to envelop the listener into a soundscape without drawing attention to itself, similar to ambient music. Examples of drone doom bands include Earth, Sunn O))), and Khanate.
Drone doom will envelop you in sound after a few seconds. It's a hell of a feeling.