A metal or metallized reinforcer, at least the surface of which is at least partially metallic, comprises at least a metallic part coated with a polybenzoxazine, the repeat units of which comprise at least one unit corresponding to the formulae (I) or (II): in which Z1 and Z2, which are identical or different, represent an at least divalent, aliphatic, cycloaliphatic or aromatic bonding group comprising at least one carbon atom and optionally at least one heteroatom selected from O, S, N and P. Such a reinforcement can be used for the reinforcement of a rubber article, in particular a motor vehicle tire.