The collective electronic polarization waves occurring in a regular two-dimensional lattice of rare gas atoms adsorbed on a metallic surface are studied, including interactions mediated by the metallic substrate. The atoms are represented as three-dimensional isotropic harmonic oscillators interacting via electrostatic dipolar forces. The polarization eigenmodes of an isolated monolayer are first determined, from which the cohesive energy of the layer can be deduced from the total zero-point energy of the modes. Then the role of the substrate is introduced by treating the metal first as a perfectly conducting medium (ε=−∞) and then, more appropriately, as a substrate of dynamical dielectric function ε (ω) =1−ω2p/ω2. The monolayer–metal interaction produces a shift of the collective atomic frequencies and of the metal surface plasmon frequencies. From the zero-point energy shift, one obtains an expression of the total interaction energy. Numerical applications are made for a square lattice of Kr adsorbed on metals of various plasmon frequencies.