Metal Containers/Metal Decoration
Never use metal or metal-rimmed cookware in the microwave oven.
Microwaves cannot penetrate metal. They will bounce off any metal object in the oven and cause arcing, an alarming phenomenon that resembles lightning.
Metal shields the food from microwave energy and produces uneven cooking. Also avoid metal skewers, thermometers, foil trays, metal-rimmed or metal-banded dinnerware, casserole dishes, etc. The metal rim interferes with normal cooking and may damage the oven.
Aluminum Foil
Avoid large sheets of aluminum foil because they hinder cooking and may cause harmful arcing.
Use small pieces of foil to shield poultry legs and wings.
Keep ALL aluminum foil at least 1 inch from the side walls and door of the oven.
Wood
Wood bowls and boards will dry out and may split or crack when you use them in the microwave oven.
Baskets react in the same way.
Tightly Covered Cookware
Be sure to leave openings for steam to escape from covered containers.
Pierce plastic pouches of vegetables or other food items before cooking.
Tightly closed pouches could explode.
Brown Paper
Avoid using brown paper bags.
They absorb too much heat and could burn.
Flawed or Chipped Cookware
Any container that is cracked, flawed, or chipped may break in the oven.
Metal Twist Ties
Remove metal twist ties from plastic or paper bags.
They become hot and could cause a fire.