Gallium (Ga)-based liquid metals (LMs), due to their good fluidity and high electrical/thermal conductivity, yield many attractive room-temperature properties different from solid metal materials and even overcome some bottlenecks that solid metal cannot reach. Therefore, Ga-LMs exhibit great application prospects in flexible devices, soft robots, and others. The unique physical properties of Ga-LMs are closely related to their atomic structures, bonding, and valence relationship, as well as their electronic properties. An in-depth understanding of the basic structure and physical properties of Ga-LMs is of great significance for the research and application of liquid metal materials. In this review, we briefly introduce the theories and analytical methods commonly used for studying the basic physical properties of liquid metal, through the aspect of the microscopic atomic structure. Accordingly, some most attractive properties of Ga-LMs are reviewed and discussed. Finally, the opportunities and challenges for the study and application of LMs are discussed as well.