Every kind of particle in nature has an antimatter counterpart—a version of itself with the same amount of mass, but with opposite values for its electric charge and other quantum properties. The proton has the antiproton, the muon the antimuon, and so on. The only exceptions are those particles with no quantum properties to change the sign of. The photon, for example, has no electric charge or other such quantities. For this reason, the antimatter counterpart of the photon is simply the photon itself.
