Alkali metal cations are commonly selected as components of the electrolyte and could greatly affect the reaction dynamics at the electrode-electrolyte interface in many different ways. Comprehending the role of alkali metal cations in electrochemical reactions is thus crucial for the optimal design of electro-cataly tic systems. However, characterization of the electrode-electrolyte interface is challenging, and approaches have been made to elucidate the underlying mechanisms of alkali metal cations in promoting electrochemical reactions. This perspective discusses the progress, challenges, and outlook of the role of alkali metal cations at the electrode-electrolyte interface involving various electrochemical, spectroscopic, and computational methods. The aim of this perspective is to help researchers understand alkali metal cation effects for the prospect of designing highly efficient electro-cataly tic systems.