Spherical silicon nanoparticles with the sizes of 100–200 nm exhibit strong electric and magnetic dipole responses in the visible spectral range due to Mie resonances. At the resonance conditions, electromagnetic energy is accumulated inside Si nanoparticles, which can be used for the realization of efficient nanoantennas, nanolasers, and novel metamaterials. In this paper, modification of optical properties of Si nanoparticles by metal nanoinclusions, randomly distributed inside them, is theoretically investigated. The method is based on the recently developed, so-called, decomposed discrete dipole approximation (DDDA) allowing multipole analysis of light scattering by arbitrary shaped inhomogeneous nanoparticles. Particularly, the influence of metal nanoinclusions, their concentration and distribution, on the excitation of magnetic and electric dipole modes in Si nanoparticles is studied.