A composition and method are described for providing conformal protective or decorative polymer coatings on metals such as aluminum, copper, iron, steel, zinc, and this by dip autopolymerization. In accordance with the present invention, an acidic solution of organic monomer undergoes autopolymerization upon contact with a metal substrate, thereby forming a polymeric coating on the substrate. The method comprises providing the acidic monomer solution, dipping the metal substrate to be coated for a prescribed period of time depending on the thickness of the coating desired, and then removing the substrate from the solution. Importantly, the polymerization requires no application of external driving force, such as thermal or electrical energy. The coatings thus formed are up to 50 microns thick, and conform to the shape of the substrate. These coatings further have uniform thickness, and excellent thermal stability and protective properties. In one preferred embodiment of the present invention, the composition comprises an acidic solution of an organic electron acceptor monomer that undergoes autopolymerization in contact with a metal substrate, thereby forming a polymeric coating on the substrate. In another preferred embodiment of the present invention, the composition comprises an acidic solution of an organic electron acceptor monomer and an organic electron donor monomer that undergo autopolymerization in contact with a metal substrate, thereby forming a polymeric coating on the substrate. Metal-polymer composites are also described.