A metal was an element, compound, or alloy.

Native to Skaro, the Magnedon was a lifeform with a body made out of a pliable metal held together by a magnetic field. (TV: The Daleks)

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)