The invention relates to protective coating systems derived from a functional polyester resin, a cross-linker and a phenol-formaldehyde resin. Also provided is a method of coating a metal substrate using the protective coating systems to produce a cross-linked protective coating. Further provided is a composite material prepared with the coating system and, in certain embodiments, useful in fabricating metal foodstuffs storage containers. The composite material may be particularly useful in fabricating foodstuffs storage containers and “easy-open” end closures wherein the cross-linked protective coating contacts the foodstuffs.