Microwaves can be reflected by metal, so they are reflected within the metal interior of the oven where they are back and forth through and absorbed by food, to strengthen the thermal efficiency. However, metal utensils should not be used in the microwave oven in case of slowing down the heating or even arcing or sparking. The Xiaomi Microwave Oven adapts cold rolled sheets, with metal grids on the oven door. Besides, the Xiaomi Microwave Oven also comes with an auto power-off when opening the oven door feature, which keeps the microwave from leakage.