The properties of infinitely dilute metal ammonia solutions are interpreted on the basis of Landau's model for electron binding by polarization of the dielectric medium. The electrons are bound in cavities of radius 3.2-3.45 A. The energy levels of the trapped electrons are computed by the variation method using one-parameter wave functions. It is possible to obtain theoretical values for the heat of solution of the electron and the energy of the 1s→2p transition in agreement with experimental data. The susceptibility of the energy of the electronic transition to temperature cannot be interpreted by the temperature dependence of the dielectric constant only, and it is presumed that the electron cavity radius is temperature dependent.