The molten salt-based direct reduction process for reactive solid metal outperforms traditional pyrometallurgical methods in energy efficiency. However, the simplity and rapidity of this process require a deeper understanding of the interfacial morphology in the vicinity of liquid metal deposited at the cathode. For the first time, here we report the time change of electrode surface on the sub-millisecond/micrometre scale in molten LiCl-CaCl2 at 823 K. When the potential was applied, liquid Li-Ca alloy droplets grew on the electrode, and the black colloidal metal moved on the electrode surface to form a network structure. The unit cell size of the network and the number density of droplets were found to depend on the applied potential. These results will provide important information about the microscale mixing action near the electrode, and accelerate the development of metallothermic reduction of oxides.