I'd love some Cosmic Metal, but almost all of what I've found is Black Metal. Can anyone suggest any Death, Power, Prog, or Heavy Metal that's very spacey/Cosmic? It should sound like the dark blackness of empty space, the scorch of a thousand stars, or anything else cool and in space like that. Also, preferably no abstract/experimental/avant-garde stuff. Thanks!

Mithras is what you're looking for, baby

Seconding Mithras. Very psychedelic and dreamlike.

For traditional metal I suppose you can try...

Sacred Blade - Of Sun + Moon
Full Moon - S/T

For death metal:

Blood Incantation - Starspawn

Thanks for the suggestions y'all! I'm definitely gonna add these to The List™.

Would Nocturnus be too obvious? Especially 'The Key'.

Vektor - thrash
Euphoria Ω - thrash
Sympuls-e - melodeath - first album kicks ass, second is okay, and third I don't really remember

The one who says "Nocturnus" must also say "Starseed", which are the German Nocturnus. Fantastic self-released MCDr.

These might be up your alley?
Blood Incantation - Starspawn (Death Metal)
Tomb Mold - Manor of Infinite Forms (Death Metal)
Timeghoul- Tumultuous Travelings & Panaramic Twilight (Death Metal)
Nucleus - Sentient (FL) & Fragmented Self (split) (Death Metal)
Tchornobog - Tchornobog (Black/Death)
Nocturnus - The Key (Death Metal)
Merkstave-Merkstave (funeral doom but kinda atmospherically spacey?)

Definitely more out there but thats what I got on top of my head.

Check Alchemist from Australia:

https://www.metal-archives.com/bands/Alchemist/42

My recs are from the Doom scene, of course:

Monolithe - Nebula Septem (doom)
Ison - Cosmic Drone (ethereal doom drone)
Until Death Overtakes Me - Symphony III (Funeral Doom)
STATION DYSTHYMIA - Overhead, Without Any Fuss, The Stars Were Going Out (Funeral Doom)

Mechina

https://www.metal-archives.com/bands/Mechina/57637