A metal was an element, compound, or alloy.
The Kiseibya were metal-eating creatures developed to be a Dalek predator. (AUDIO: Enemy of the Daleks)
Gallifreyan zinc was one of the strongest metals in the universe. (AUDIO: Pier Pressure)
Photavine steel was a metal used in Tritovore ships. When it heated up, it cooled down the interior of the ship. (TV: Planet of the Dead)