Fire resistant lightweight cladding 10 comprising thin sheet material having an outer layer which is predominantly steel and a thicker inner layer which is predominantly aluminium, the inner layer being a supporting layer and the sheet material being formed into a panel of predetermined outline and used in a fire-resistant wall panel assembly comprising a substrate supporting outer cladding sheets in side by side relation, each cladding sheet being a composite of a relatively thin steel layer and a relatively thick aluminium layer, the sheets described herein have a steel outer layer which is about 4 mm thick and an aluminium layer is about 2 mm thick and panel density from 6 kg/m2 to 9 kg/m2. The panels were tested according to British Standard BS 8414-22015 (amdt 1) as modified by Australian 5113-2016 (amdt 1) and the specimen passes the classification criteria 5.4.4(b) which concerns the temperature differential from outer fireside and inside and 5.4.5(g) which concerns debris.