First of all, from the perspective of food safety, the plastic wrap commonly used in general families is not heat-resistant, and the grease in food can easily dissolve harmful substances such as plasticizers in plastic wrap.
However, from the perspective of electrical safety, if the plastic wrap is not covered, the steam and oil in cooking will pollute the inner wall of the microwave oven after being heated and evaporated, and in severe cases, too much oil will accumulate on the inner wall, which will lead to a fire. Therefore, when hot dishes, especially those with soup, it is best to cover the special cover of microwave oven with glass to avoid unnecessary troubles such as short circuit of microwave oven caused by too much steam.
If there is no special cover for microwave oven at home, of course, you can also use the plastic wrap available for microwave oven, but when using plastic wrap in microwave oven, you should try to avoid food contact with the film, especially oily food. When heating food, the plastic wrap covering the utensils should be perforated to avoid cracking. When using, we should also pay attention to the temperature that plastic wrap can withstand when heating, and heat it in strict accordance with the temperature marked on the package or choose plastic wrap with good heat resistance. Even the polyethylene (PE) plastic wrap is marked with the words "can be used by microwave heating" or "can be used at high temperature", but it should be used with caution, because up to now, there is no authoritative test data showing that it is safe to use PE plastic wrap under such conditions.