Curable powder film-forming composition exhibiting improved flow and leveling

A curable powder film-forming composition is provided, comprising (i) 5 to 95 percent by weight based on the total weight of the film-forming composition of a crosslinking agent; (ii) 5 to 95 percent by weight based on the total weight of the film-forming composition of a polymer containing a plurality of functional groups reactive with the crosslinking agent; and (iii) particles having a mean particle size less than 100 nm. The particles are substantially free of functional groups on the particle surface, and are present in an amount at least sufficient to improve the flow and leveling of the composition when applied to a substrate and cured, as measured by longwave scanning, compared to a similar cured coating without the particles. A multi-component composite coating composition is also provided, comprising a pigmented basecoat and a clear coat. The basecoat and/or clearcoat may be derived from the curable film-forming composition described above. Also provided are coated substrates in which the curable coating compositions or the multi-component composite coating compositions described above are applied to a substrate and cured to form a cured coating.