In recent decades, new materials have come into use for modern sculpture. Various types of iron and steel and aluminum alloys are preferred. The artist rarely knows precisely the type of metal and almost never is aware of its weathering behavior. With bronze, a patina develops gradually. On iron, steel and aluminum sculpture, considerable damage is evident a short time after exposure. With financial support by the Deutsche Forschungsgemeinschaft, a large number of sculptures made from these metals were examined in order to list systematically the types of damage, and propose techniques of conservation and maintenance.