The NA60 experiment studies muon pair production at the CERN SPS with proton and Indium beams. It is a second generation experiment, designed to answer specific questions left open by the previous round of SPS experiments, finished in year 2000. The results presented in this talk include the in-medium modifications of the $\rho$ meson, the origin of the dimuon excess observed between the $\phi$ and J/$\psi$ peaks, and the study of J/$\psi$ suppression. In each of these subjects the NA60 results represent a significant step towards a deeper understanding of the physics of heavy-ion collisions at SPS energies.