The saturation coverage of molecules adsorbed on metal surfaces is often seen to increase with temperature of adsorption, and may be accompanied by the ordering of the molecules into periodic structures at higher temperatures. The case of NO on Rh(111) presents a specific example of this behavior. Modelling the adsorption process by means of Monte Carlo simulations in which diffusion and lateral interaction are considered indicates that both the increase of the saturation coverage and the ordering with increasing adsorption temperature are in agreement with an enhanced mobility of the adsorbed molecules