The Maxwell Garnett effective medium theory was originally developed for a very small volume fraction of metal particles in a transparent medium. In contrast to the bulk situation, it can be applied to high coverages for thin metal particulate films and predicts the plasmon resonance energy accurately in contrast to the Bruggeman effective medium theory. The comparison of the Maxwell Garnett approach to a more rigorous analysis of particulate films with the Thin Island Film theory shows that also the plasma energy of the plasmon resonance is very accurately obtained with the simple effective medium theory. Also a quite accurate splitting of the resonance energy through particle interaction is obtained. However, interband transitions and the optical coupling of the layer with the effective medium response to the substrate lead to substantial differences compared to the dipole approximation of the rigorous Thin Island Film theory.