To provide a top coating material which can give a coating film having a very high hardness as high as 9H and recovery by washing simply by baking and is suited for interior tunnel plates and to provide a metallic plate coated therewith and used as an interior tunnel plate.

This material contains 0.1-30wt.%, based on the resin solid content, alumina having a mean particle diameter of 1-30μm and 0.1-10wt.% boron nitride having a mean particle diameter of 0.01-10mm in a resin solution (e.g. siloxane resin solution). A metallic plate is subjected to formation treatment (e.g. chromate treatment), priming and optionally coating with an intermediate coating material and lastly coated with the top coating material to form a coated metallic plate.