What are some fictional metals or materials you've used in your campaigns?

Okay, I'll try to explain : in my setting (alternate reality milky way with more awesome poured into it), some legendary weapons are made out of solid light. Now you think that it's not a metal but it's actually found, not created/generated, and mined in random ass asteroids. It's weightless (litterally), and, aside from being uber-radioactiv, not really harmful, unless refined. Then, through various means, the material actually become partly immaterial and can go through stuff, damaging it in the process. Lightsabers are not a thing, but weapons using modified non-solid light are only "coated" in it

How'd you get rid of it once it takes hold?And what if you expend all your spells, every day? Does it wither because it's got no food, or does it sustain itself on ambient magic?

Uber Radioactive
Not very dangerous.
Pick one user.

Contradictions aside that's gotta be the best explanation for brilliant energy weapons.

cooking
smelting
heating buildings
survivalism
welding

Thundersteel. It's super light and super strong- a man has difficulty even telling that he's holding a thundersteel dagger- but it can only be made by a wizard capable of manipulating lightning.

Or at least that's what the players think. It's actually just aluminium.

Well, radiation is not something that dangerous in a setting were space wizard can ward you from it.
Also, there's much, much worse than that out there, it's kinda hard to talk about stuff sans bursting into >muh lore exposition
But yeah, I would advise player not to eat that stuff.

super-radioactive could be a little bit misleading....you could say that it quickly dissipates/degrades into non-harmful light unless refined....

>>top kek

Bloodsteel, the proof of a great warrior, it only happens when any piece of still goes through a bloodshed multiple times. It's until unknown whether objects made of this material do hold some power and characteristics or it's the wielder's abilities and power shining through those artifacts.

SoS's premise for Orichalcum was pretty cool, but setting specific. A metal that cannot be deformed or damaged so long as any living thing is in contact with it. When not in contact, it's as malleable as gold, making it easy to work. It's only ever found native in subterranean deposits shaped like eyes, with each deposit "looking" in the direction of another, possibly hundreds of miles away.

People use it to make swords and armor of impossibly thin dimensions that are nevertheless indestructible as long as someone is holding them, or to uphold impossible buildings with wire-thin strands which are kept connected to a bucket of mice or something, so that they can never break.

doesn't make it less dangerous but i get what you're saying. Cause if you're mining an asteroid in mid evil fantasyville you better have a godamned wizard.

I have something called Bloodsteel too.

Except it's a cursed material so rough and jagged, no matter how much you try to grind it or smooth it or mold it, touching it flays the flesh and causes immense bleeding.

You know how fucked up shit has to be when getting hit by a maul will make you bleed worse than a sword?

And gods help you if you get a sliver embedded into your skin.