The outcome of many catalytic processes can be altered dramatically by an introduction of a small amount of alkali promoters. These promoters can speed up certain elementary reaction steps, slow down a particular step, or neutralize catalytic sites that lead to undesired products. We have employed Density Functional Theory (DFT) calculations to investigate the impact of alkali adsorbates on various elementary reactions on metal surfaces. We demonstrate that alkali adsorbates induce a substantial electrostatic potential along the z-direction (normal to surface) and significant dipole-like electric fields in the vicinity of the substrates. We show that the alkali-induced electrostatic potential significantly alters the chemical behavior of the metal substrate. We also show that operating pressure and temperature, i.e., the gas-phase chemical potential of reactants might impact the promotion mechanism.