I never understood these music genres

[PuPu]

Black
Death
Doom
Folk
Power
Progressive
Thrash
Traditional

These are legit and the differences between them are clearly defined. These are essentially the only metal genres. (There are actually more subgenres of death metal, but have differing characteristics)

Drone
Sludge
Stoner

Other ways of saying doom metal. Kind of like "emo" and "scremo" with post hardcore.

Neo-classical
Symphonic

Classical and symphony music played with metal instruments

Speed

Another way of saying thrash metal

Avant-garde

Another way of saying progressive metal

Extreme metal

Umbrella term used for Black, Death, Doom, and Thrash

Grindcore

Hardcore punk influenced by thrash or death metal

Glam
Industrial
Metalcore
Nu Metal

False metal. Not actual metal genres.

Alternative
Gothic
Groove
Christian
Crust Punk
Funk
Viking

Stupid terms that don't list any musical characteristics and have practically nothing to do with the music itself.