We have proposed microscopic models for describing the multiferroic properties of BiFeO₃ and GaFeO₃. It is shown that the mechanisms of the multiferroism are different. In BiFeO₃, the magnetoelectric coupling is biquadratic, whereas in GaFeO₃ it is linear. The site disorder between Ga and Fe is a primary source of the net magnetic moment in GaFeO₃. The temperature and magnetic field dependence of the polarization is calculated in order to show that the proposed models for these two multiferroics are correct. Near the magnetic phase transition temperature T_N we obtain a kink in the electric properties.