We present here some of the first results we have obtained on the study of the optical spectra of Spitzer/MIPS 24 micron-selected galaxies in the COSMOS field. This is part of a series of studies we are conducting to analyse the optical spectral properties of mid-infrared (mid-IR) galaxies with different IR luminosities up to high redshifts. The results shown here correspond to the brightest S(24 micron)>2 mJy IR galaxy population at z<1.