Electrochemical reduction of CO₂ to CO using renewable energy is one of the effective ways to achieve "carbon neutrality" and renewable energy storage.This review briefly described the advantages and basic principles of the electrochemical reduction of CO₂ and summarized the research progress of metal electrocatalysts for the electrochemical reduction of CO₂ to CO in aqueous solutions in recent years.Specifically,this study mainly introduced the recent research progress of mono?metal nanocatalysts,bimetallic catalysts,metal?organic complex catalysts,and mono?atom catalysts,which included their influences on the electrochemical reduction of CO₂ and relevant reaction mechanisms.The introduction was conducted from several perspectives,such as the preparation of nanoparticles as well as the regulation of their composition and structure,alloy construction,structural design of metal centers as well as their ligands and carriers,and the development of mono?atom catalysts. In addition, this study summarized the advantages and disadvantages of various catalysts and predicted the development trend of metal catalysts.