A substantially radiation absorbing layer of metal having a microstructured surface characterized by a plurality of randomly positioned discrete protuberances of varying heights and shapes, which protuberances have a height of not less than 20 nanometers nor more than 1500 nm, and the bases of which contact the bases of substantially all adjacent protuberances is disclosed. The metal layer, which may be a coating on a variety of substrates, is useful as a radiation absorber (particularly solar). A method is disclosed for producing such layers.