The absorption mechanisms of Poisson-distributed disordered Metal-Insulator-Metal structures are investigated theoretically and numerically. In particular, from the Poisson point process, Slivnyak-Mecke integrals are used to predict the number of isolated particles and majority clusters as a function of the particle density z. Then, the impact of these numbers on peak, mean, and bandwidth absorbance is calculated by full-wave electromagnetic analysis. It is shown that the peak absorbance reaches a maximum value of higher than 0.9 for a particle density of 0.6 cm-2 originating from main contributions of monomers and dimers whereas trimers represent less than 6% of the total number of particles. The conclusions of these studies are experimentally confirmed by means of free-space characterization.