Gallium-based liquid metal (GLM) is an amorphous metal that remains liquid at room temperature. It has important characteristics, such as high temperature resistance, high thermal conductivity, good electrical conductivity, favorable radiation resistance, and low saturated vapor pressure, and is thus an ideal lubricant in nuclear equipment, aerospace industry, and other engineering fields under extreme operating conditions. First, the physicochemical properties and the factors affecting the lubricity of GLM are reviewed in this paper. Furthermore, the lubrication mechanisms of GLM are elucidated in detail. Then the research progress in strategies to improve the lubricity of GLMs is summarized. After that, the applications of GLM in engineering tribology are also reviewed. Finally, the future developments of GLM as a special lubricant for extreme conditions are proposed.