Copper was a metal familiar to the smiths of Middle-earth. Mahtan, the father of Nerdanel (the wife of Fëanor), prized this metal above gold. He wore a band of copper about his head and was known as Urundil or "copper-lover".
Other Versions of the Legendarium
Copper was one of the six metals used by Aulë to create the alloy Tilkal. It was used to forge the great chain Angainor to bind Melkor. In a footnote, it was explained that "tilkal" was an acronym formed from the initial letters for each of the six metals. The first letter, 't' came from tambë, which was apparently the word for "copper".