This paper addresses the key requirements for fusion materials, as these have emerged from studies of commercial fusion power plants. The objective of the international fusion programme is the creation of power stations that will have very attractive safety and environmental features and viable economics. Fusion power plant studies have shown that these objectives may be achieved without requiring extreme advances in materials. But it is required that existing candidate materials perform at least as well as envisaged in the environment of fusion neutrons, heat fluxes and particle fluxes. The development of advanced materials would bring further benefits. The work required entails the investigation of many intellectually exciting physics issues of great scientific interest, and of wider application than fusion. In addition to giving an overview, selected aspects of the science, of particular physics interest, are illustrated.