Complex sentence: Adamantium is a fictional metal alloy First Mentioned in the Classic 1956 Scifi movie Forbidden Planet then years later appearing in American comic books published by Marvel Comics, and is best known as the substance bonded to the character Wolverine's skeleton and claws.
Split into simpler sentences: Adamantium is a fictional metal alloy first mentioned in the 1956 movie Forbidden Planet then, years later, appearing in American comic books published by Marvel Comics. It iss best known as the substance bonded to the character Wolverine's skeleton and claws.