Ice coating caused by ice and snow disasters is extremely harmful to DC power grids. Therefore, the research and application of ice melting technology are of great significance for DC grids to combat with ice disasters. In normal operation, the current of metal return is zero and does not have an anti-icing effect, so it is especially important to discuss it. The paper uses the thermal effect of current to melt the metallic return. Firstly, the critical ice-melting current of the metal return in the four-terminal flexible DC grid and the ice-melting time corresponding to different melting currents are calculated, and the power flow calculation model of DC grid with metallic return is established. The paper innovatively uses the bipolar converter station power reversed method to melt the metallic return, selects different ice-melting conditions, and analyzes the ice-melting of the four-terminal power grid to obtain the most suitable ice-melting conditions. The simulation analysis of the ice-melting control process is carried out. Finally, it is concluded that the bipolar reversed power mode is more suitable for melting the metallic return, which can realize ice-melting without power failure and has less power requirement for the converter station.