I Need a Subgenre Checklist

I tend to classify bands in more generic terms.

fast vs slow
dark vs light
repetitive vs flowing
technical vs emotional
serious vs carefree
degree of heaviness
traditional melodies vs ethnic or progressive, etc.

Some fit better with others than not. Slow/dark/repetitive/emotional/serious/neutral heaviness/ethnic or progressive sums up my interests in BM, post, doom, and folk. While just the opposite seems to interest me in bands more like Clutch, Karma to Burn, etc.
 
My itunes classification goes
heavy metal (heavy/doom/thrash)
rock (any type of rock/sludge/southern/stoner metal/whatever other oddities i listen to that arent metal)
death metal
black metal

I've found that trying to overclassify music on something like that causes a headache. it's fine to try and find something you like, but to have 100 different genres with one album each is cluttery, imo.

That's a pretty good way to look at it. Metal, metal that focuses on darkness, metal that focuses on heaviness, and music that's similar to, but not, metal. Then for some of the outliers like folk or progressive, that's just more of a particular take on one of the existing genres. IE less traditional melodies/song structures leaning either towards ethnic or experimental roots.
 
I like your method, Draele. I think I'm going to make my own checklist of fast/slow/etc. and make my own genres. I just split up all my 'rock' bands- now I have rock, alternative rock, hardcore, and nu metal (yeah, those were all just listed as rock).
 
My Itunes is sorted as follows;

* Thrash Metal (includes Thrash/Death)
* Black Metal
* Death Metal (Blackened, OSDM, Brutal, Technical etc)
* Melodic Death Metal
* Doom/Gothic Metal (Only contains Traditional Doom & Gothic/Doom crossover - Death/Doom is filed under Death Metal)
* Heavy/Power/Prog Metal
* Folk/Viking Metal
* Avant-Garde Metal
* Industrial Metal