Lustre is the property of surface of substance to reflect light due to which substance appears shiny. For example, iron, copper, aluminium, gold, silver, etc. Metals have highly shining surface and thus possess a good metallic lustre and are used for making ornaments.

A material is brittle if, when subjected to stress, it breaks without significant deformation. Brittle materials absorb relatively little energy prior to failure, even those of high strength. Breaking is often accompanied by a snapping sound.

Alloys are metal mixtures with other elements, the precise combination of which is governed by the properties required. In general, alloys are considered metallic in nature, i.e. they have good thermal and electrical conductivity. An alloy is a homogeneous mixture of two or more metals or a metal and a nonmetal.