Yes, aluminum can melt or cause fires in a microwave oven. Microwaves work by generating electromagnetic waves that excite water molecules in food, causing them to vibrate and produce heat. While most microwave-safe materials, like glass and ceramics, allow the microwaves to pass through them without any issues, metal objects, including aluminum, react differently.
Aluminum is a good conductor of electricity and can reflect microwaves rather than absorbing them. When you place aluminum foil or any aluminum-containing item in a microwave oven, it can cause a build-up of electric currents on its surface. The rapid increase in current density can cause the aluminum to become very hot, leading to melting or, in extreme cases, sparking and causing a fire.
For safety reasons, you should never put aluminum foil or any other metal object inside a microwave oven. Additionally, avoid using aluminum trays or containers that are not explicitly labeled as safe for microwave use. Always follow the manufacturer's instructions and use microwave-safe materials when cooking or heating food in a microwave oven to prevent potential hazards and damage.