This study investigates the Natural circulation loop phenomena of three liquid metals gallium, lead–bismuth, and sodium–potassium commonly used in advanced cooling systems, particularly for natural circulation in reactors. It is observed that gallium exhibits a linear increase in mass flow rate with power density, offering good thermal conductivity, though requiring careful temperature control due to its low boiling point. Lead–bismuth, while requiring a steeper increase in mass flow to overcome its higher viscosity, provides excellent heat transport capacity and is effective in natural circulation systems. Sodium–potassium, characterized by the fastest increase in flow velocity, excels in heat transfer efficiency but necessitates high flow rates to maintain stable circulation. Among the three, sodium–potassium is the most efficient in heat transfer but demands the highest flow rates to ensure steady-state circulation. Lead–Bismuth tends to be the most optimized in terms of thermal properties and stability, particularly in high-temperature systems like nuclear reactors. Gallium is more suitable for lower-temperature applications. The findings indicate that among the three metals, sodium–potassium demonstrates the highest heat transfer efficiency. Gallium, as a coolant, offers superior natural circulation capability and stability, followed by lead–bismuth, with sodium–potassium being the weakest in this regard. However, overall, the natural circulation capabilities of all three metals are inferior to that of water.