Rates of chemical reactions on metal surfaces are simulated using a dynamic Monte Carlo formalism. The initial emphasis is on the adsorption step, with an attempt to predict the formation of islands and other nonstatistical patterns caused by adsorbate-adsorbate interactions, and on the effect of such interactions on the apparent (experimentally observable) activation energies of bimolecular reactions. The work will be extended to thermal desorption systems as well. The ability to predict to effects of index plane on the rates of various surface processes would be of great help both in the design of new selective catalysts and in the design of catalytic reactors.