[renholder]

Just to note: Some death-metal bands have positive lyrics[0,1]... (Though, whether they can really be called a death metal band is possibly a point of contention.)

[0] - https://youtu.be/lk2-bgwA0Ro

[1] - https://youtu.be/Nh10gL_GP_w

[soheilpro]

Some examples with science-themed lyrics (not all "death metal", though):

Avenged Sevenfold - Fermi Paradox: https://www.youtube.com/watch?v=vl8rofNa0tI

Avenged Sevenfold - Exist: https://www.youtube.com/watch?v=ntgOlFbGWLY

Nightwish - The Greatest Show on Earth: https://www.youtube.com/watch?v=IJb3xwtpmmc

Nightwish - Endless Forms Most Beautiful: https://www.youtube.com/watch?v=VUb1p8fm7Ag

Dream Theater - The Great Debate: https://www.youtube.com/watch?v=4z6vpiXQJNA

Allegaeon - Gray Matter Mechanics: https://www.youtube.com/watch?v=tu-NvEec8y8

Allegaeon - All Hail Science: https://www.youtube.com/watch?v=ONPMWHP8AZ4

[mcv]

I think those are more towards the symphonic end of the metal spectrum. They tend to love science, SciFi, but also fantasy.

[motohagiography]

Not only do they have positive lyrics, some even have comforting recipes[2]

https://youtu.be/xwksxDHNoAE

[renholder]

I don't know why but I half-expect that to be a ROSMT[0] link.

[0] - https://youtu.be/OvW2xeSn4As

[hi5eyes]

tgi definitely have positive lyrics, most modern melodic hc bands do, but they are definitely hardcore and not metal

[stringyham]

Can't mention positivity without linking Lykathea Aflame [0]

[0] - https://www.youtube.com/watch?v=8IEqf9mo93w