Hey,
What are the best band you know that talk about science fiction franchises (I prefer Black Metal, but i'll take anything) ?
Thank you !

Definitely the opposite of what you're asking for genre-wise but Helion Prime is a power metal band with songs about Star Trek, 2001: A Space Odyssey, and others.

I'd recommend Bal-Sagoth, my man. Symphonic black metal that deals heavily with science fiction. They're an amazing band to boot.

hoth do star wars themed melodeath - the last album (oathbreaker) was fantastic

erm, this makes me think of the almighty vondur:

Concept album, "that follows the story of an individual from his conception and follows him down a path that grows darker and darker."

Jesus Christ guys, it's obviously about Darth Vader. Not that I'm talking shit, I've tried multiple times to write lyrics about Star Wars but I could never pull it off, and these guys cranked out an entire album about it, drawing from the prequels no less.

Star One - Space Metal (2002) & Victims of the Modern Age (2010)

The debut one includes songs about Dune, Star Wars, Star Trek, Alien, 2001 etc... And the second is about dystopia sci-fi movies (12 Monkeys, Escape from New York [how feaking cool is that?!?!?!], Blade Runner etc...).

This is Arjen Lucassen's project with (surprise, surprise) guest vocalists like Russell Allen, Floor Jansen, Dan Swanö etc. It's (progressive) heavy metal, morelike, though.

Manticora - Hyperion

Progressive/power metal based upon the novel Hyperion by Dan Simmons.

I never took the time to read Empyreal Regime's lyrics, but the tech-death band Xenomorph is....well they're named Xenomorph and the cover is the xenomorph alien from the film....so I can only imagine they're somewhat inspired by the Alien franchise if nothing else at least aesthetically? Not a bad album either. Reminds me of Embryonic Devourment.

also notable for having bill taylor (immolation 2001-2016) on it... one of my favourite finds from the osdm gems thread we had a while back; an absolutely charming album

Xenomorph (USA) is criminally underrated Alien-inspired death metal: https://www.youtube.com/watch?v=8v4te-n8iSY

I feel I should mention To Tame A Land just because someone needs to

Metroid Metal does covers of songs from the series Metroid. Good instrumental metal that can even appeal to people unfamiliar with the video games.

I'm not the biggest tech death fan, but I'll jump in with the voices recommending Xenomorph. Not an overlooked masterpiece but definitely worth your time.

When I think of Sci-Fi franchises + Metal the Bolt Thrower is absolutely number 1, there was also this old school band "Detest" I think their lyrics might be related some sci-fi book, it says "Lyrical themes:
Ongoing science-fiction concept". If I remember correctly some joke/parody black metal about Darth Vader exist as well.