Establishing simple and physically transparent models for the analysis of the interactions between adsorbates on surfaces is critical for unearthing the underlying mechanisms of promotion and poisoning in heterogeneous catalysis, for understanding the nucleation and growth on surfaces, as well as for the development of predictive theories of materials and catalysis. In this project we are investigating the underlying mechanisms that govern adsorbate-adsorbate interactions on surfaces, with an emphasis on alkali promotion in chemical reactions on metal surfaces. Alkali promoters (Li, Na, K, Rb, Cs) enhance activity and/or selectivity of various catalytic processes. These promoters are utilized in Fisher-Tropsch and alcohol synthesis, water-gas shift reactions, ammonia synthesis, olefin epoxidation, automotive three way converters. Although the impact of alkalis in heterogeneous catalysis has been recognized for decades, not much is known about the underlying physical mechanisms that govern the alkali promotion. We have employed Density Functional Theory (DFT) calculations to develop a very general and physically transparent framework that allows us to identify the underlying mechanisms that govern adsorbate-adsorbate interactions on surfaces. Within this framework the adsorbate-adsorbate interactions can be classified in terms of (i) the electrostatic interaction between the regions dominated by the adsorbates, or (ii) through-surface or direct electronic communication between the adsorbates. 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.