Which fictional metal makes Bilbo’s sword Sting glow near Orcs in Tolkien’s works?

No specific metal is stated to make Bilbo’s sword Sting glow near Orcs in Tolkien’s works.

Sting is an Elvish blade found by Bilbo Baggins in a troll hoard during The Hobbit. Like the swords Glamdring and Orcrist, it shines with a blue light when Orcs or goblins are nearby. Tolkien describes the blades’ behavior, but does not identify a special metal as the cause of the glow.

Mithril is a famous fictional metal in Middle-earth, and it is associated with Bilbo’s coat of mail. It is not identified as the material of Sting. This distinction makes the question easy to confuse with other details from the same story.

Sting later passes from Bilbo to Frodo, who uses it during the journey to Mordor. Its glow provides an early warning in dark places, while its small size suits a hobbit even though it is technically an Elvish sword.