Adamantium

Adamantium is a fictional, indestructible metal alloy. In the Marvel Comics Universe, it is best known for being the substance bonded to the character Wolverine's skeleton and bone claws.

Read more about Adamantium:  Etymology, Fictional History and Properties of Adamantium, Polymorphism, Adamantium As Key Component, Adamantium in The Ultimate Marvel Universe, In Other Media