The luster of a metal is due to presence of free electrons. luster is the way light interacts with the surface of a crystal, rock, or mineral. The word traces its origins back to the latin lux, meaning “light”, and generally implies radiance, gloss, or brilliance. A range of terms are used to describe lustre, such as earthy, metallic, greasy, and silky.Luster is said to be an iridescent metallic film produced on the surface of a ceramic glaze. The electron is a subatomic particle, symbol e- or ß-, with a negative elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no known components or substructure.