The formation of metal nanoparticle coatings on oxide nanospheres, aimed at forming core-shell structures, having novel optical properties that may be tuned by variation of core size and shell thickness, has been explored. First, on non-planar oxides terminating hydroxyl groups were replaced by aluminium-hydrogen surface complexes to enable controlled reduction of metal complexes applied by impregnation from solution. Generally, very small metal particles are formed with sizes around 2 nm. Second, thermally unstable organometallic precursors were applied to polydisperse oxide spheres by impregnation from solution leading via organometallic surface complexes to the formation of uniformly arranged metal particles with sizes around 2.5 nm. At Pt nanoparticles prepared this way quantum size effect was evidenced by magnetic resonance measurement (CESR). Third, a systematic study comprised the coating characteristics of Ag and Au nanoparticles formed by surface-mediated reduction of metal salts, applied by incipient wetness impregnation, making use of the high surface hydroxyl content of monodisperse silica nanospheres. A dense population of uniformly arranged, rather small particles having a narrow size distribution is found on silica nanospheres upon drying at temperatures around 70°C. It is for the first time that metal particle formation at such low temperatures on oxide support without applying external reducing agents or media is reported. The particles are single crystalline below about 5 nm in size and exhibit cuboctahedral shape. Larger particles may exhibit lattice defects and shape deviations. The optical properties of these materials correspond to their overall structure of nanoparticulate composites having a very low filling factor of the metal phase. With higher metal loading and increasing particle size, diminishing the effect of resonance damping, the optical absorption reveals the signature of resonances due to metal particles.