Elemental Metals are WIP and it's yet not sure, if the will be implemented in the mod. Each Ore from this category is assigned to an element and it's suspected, that each of them can only spawn in a certain biome.

Armor and Weapons made out of this metals will have specific special-abilities appropriate to the element of the used metal.[1]

The Elemental Metals are: (as leaked by Shadowclaimer [2])