[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.