NOVELTY - A metal-resin composite (1) comprises a metal substrate having concavities in the surface; a first coating layer on the surface of the metal substrate; where the first coating layer fills concavities and covers the surface of the substrate; a second coating layer on the first coating layer; and third coating layer on the second coating layer.    USE - As metal-resin composite used in battery (claimed), in electric and information technology industry.    ADVANTAGE - As the first and second layers are both formed from polyphenylene sulfide resin, they can bond with each other closely, thereby overcoming the difficulty of applying a second polyphenylene sulfide resin layer on the first layer. The polyphenylene sulfide resin is directly applied onto metal substrate as a result it rapidly cool down and solidify when it contacts with the metal substrate. The rapid solidification also prevents the resin from penetrating into the ultrafine concavities in the substrate surface. There is no gas leakage under a pressure of about 10 atm.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) preparing a metal-resin composite involving etching the surface of a metal substrate, preparing a slurry, applying the slurry on the surface of the metal substrate, calcining the metal substrate to form a first precast composite, preparing a mixture, applying the mixture onto the precast composite, calcining the first precast composite to form a second precast composite, and applying a polymer onto the second precast composite by an injection molding process to form a metal-resin composite, where the polymer is selected from polyphenylene sulfide resins, tetrafluoroethene-perfluoroalkyl vinyl ether copolymers; and    (2) battery comprising a shell, a core displaced in the shell, an electrolyte, and cover plate closing the shell, where the cover plate comprising a metal substrate having concavities in the surface, first coating layer on the surface of the metal substrate, where the first coating layer fills concavities and covers the surface of the substrate, second coating layer on the first layer, and third coating layer on the second layer.    DESCRIPTION OF DRAWING(S) - The figure shows a side view of battery cover plate from a composite.    Metal-resin composite (1)    Metal electrode (2)    Metal (3)    Components for securing parts of cover plate (4)