A metamaterials is an artificially engineered structure having stop bands (or band gaps) that are frequency bands in which waves cannot propagate. Taking advantage of the stop band the vibration isolation and wave focusing become possible. Using these phenomenon of metamaterial, this paper presents applications of the metamaterial for improvement of vibro-acoustic performances of mechanical systems. Based on the vibration isolation the possibility of structure-borne noise reduction is presented. Furthermore, based on the wave focusing phenomenon the improvement of radiation efficiency of flat panel speaker is presented.