It is to provide fine particles of copper, nickel or palladium hydride having an average particle diameter of at most 50 nm, which are hardly oxidized in the atmosphere and are excellent in storage stability and are thereby very suitable for formation of metallic materials, and their production process. Further, it is to provide a dispersion containing fine particles of copper, nickel or palladium hydride, which is excellent in storage stability, and a metallic material obtained by applying the dispersion, followed by baking. The fine particles of copper, nickel or palladium hydride and the dispersion thereof, to be obtained by the present invention, are applicable to various applications, and they can be used for e.g. formation and repair of printed wiring, etc. employing a dispersion, interlayer wiring in semiconductor packages, and joining of printed wiring boards and electronic components.