A skilled smith in Valinor, Mahtan learned the arts of metal and stone work under the Vala Aulë, and for this Mahtan was also called Aulendur ("Servant of Aulë"). He wore a copper circlet around his head and was known for his fondness for the metal. Mahtan in turn taught Fëanor, the greatest of all Elven craftsmen, who—to Mahtan's regret—used this knowledge to forge the first weapons and armour in Valinor.
Mahtan had a beard, which was unusual for an Elf, especially one as young as he. According to Tolkien, most Elves could only grow beards from the "third cycle" of their lives, while Mahtan was an exception in being only early in his second. It is unclear what these "cycles" actually refer to. Mahtan's name seems to come from an old root mahta-, meaning "to handle", with special reference to the arts and skills of making.