Abstract: Composite metal panels comprise two parallel plates 1, 2 each laser-welded to an internally sandwiched corrugated stiffener plate 3. Typically, all the welds 6a, 6b are in the same sense; firstly, penetrating laser welds 6b are made along and through the troughs 5 of the corrugations into (or, less preferably, through) an underlying plate 2 and secondly welds 6a are made along and through an overlying plate 1 along and into or through the peaks of the corrugations 4. Such a panel can be readily fabricated into large-scale metal constructions, especially ships.