Metal and enamel can't be used for cooking utensils in microwave ovens, because metal can reflect microwaves. It not only causes the heating efficiency of microwave oven to decrease and the heating uniformity is poor, but also makes the microwave contact with metal to generate sparks, which is dangerous and even damages the magnetron.

Microwave ovens are usually insulated with tin foil. For example, put a glass of water and an ice cube wrapped in tin foil in the microwave oven, and then the water boils, but the ice cube hardly melts.

Tin foil can reflect microwaves. If you need to cook food for a long time, evenly wrap the food that is easy to cook with a small amount of tin foil. After cooking for a period of time, remove the tin foil and continue cooking, so that the food can be cooked more evenly. But when in use, the smooth part should be close to the food to reduce the reflected energy. Because there is no microwave component, the barbecue function can be used.