Uru is a metal ore found exclusively in the Asgardian realm. It has a natural affinity for magic, as it is readily capable of holding enchantments, absorbing magic, and channeling magic. Mjolnir is made of Uru.
Uru metal is only used by Asgardians and possibly other magic level civilizations, Uru is very durable and even more so when enchanted. It has a rock-like appearance and properties of metals. Its luster resembles badly-wrought iron. It is very absorbent of energy, especially magic. It retains enchantments well and is often used in magic. Its ability to redircet and enhance energy, especially magic, is useful and sought after. A sort of symbiotic relationship between the metal and its wielder may develop, either naturally or enhanced through magic.