The article introduces an analytical model for light transmission through metal-insulator-metal cavity arrays featuring an in-plane mirror-symmetry plane. The model involves three intrinsic parameters: eigenfrequency, radiative and non-radiative decay rates, describing the basic dynamics of the leaky eigenmode. The off-resonant response of the structure is described by two additional parameters which account for the direct light scattering process, i.e. transmission without resonant excitation. In the regime of negligible inter-cavity coupling, the intrinsic parameters are shown to be related to geometrical parameters by simple relations, while the direct transmission is found to be mostly governed by the spacing between cavities.