I was lucky enough to be an extra in the first set of Lord of the Rings movies and (at least for the chain mail) the armour they produced was "real". As in, people actually made A LOT of chainmail out of interlinked rings for the production. The way he's mentioned scale mail not correctly hanging on the body wouldn't have been an issue where chain was used in the first few movies (although I'll admit they probably made it out of a lighter material then real chain, it was still quite heavy however)
The other armour used was made from real metal (aluminium maybe?) if you were close to the camera (termed "Hero" armour) and if you were further back it was a softer sort of plastic. In particular the Helms Deep elf costumes had this plastic armour as a sort of skirt and we were constantly getting in trouble for sitting on it and bending it out of shape.