All I can think of is Arms & Equipment book which contains a table for alternate armour materials? There are such materials as Dwarven Cinder, Elfen silk (obviously not a metal), steel (assuming iron is the more common basic material?) and 'wondrous metal'. The book conveniently avoids describing or giving stats for wondrous metal, unless those are given in the errata?
Nothing about special metals in the weapon section, I think?
EDIT: ah yes, wondrous metal is defined in the errata.