A method of forming a metal pattern comprises: (a) providing a substrate; (b) depositing at least one patterned metal layer which includes a metal selected from an inert metal, an inert metal alloy, and combinations thereof; (c) disposing the substrate and the patterned metal layer in a vacuum chamber, vacuuming the vacuum chamber, and introducing a gas into the vacuum chamber; and (d) applying microwave energy to the gas to produce a microwave plasma of the gas within the vacuum chamber so that the patterned metal layer is acted by the microwave plasma and formed into a plurality of spaced apart metal nanoparticles on the substrate.