What type of materials ARE allowed in a microwave?

Question

What type of materials ARE allowed in a microwave?

Answer 1

Objects that are NOT allowed in:

1) objects that will  be destroy during the cooking process.

2) and especially objects that will  catch fire or start spreading toxic liquids or gases.

otherwise:

food, water, in safe containers, like glass, special plastics, china (ware), porcelain, ...

Answer 2

Foods and only foods contain non metal package. Any metal can cause short circuit to the microwave at that frequency. Small metal turns into sparking like the metal painting in a china. Large object like a spoon turns into burning hot and the microwave generator weakening into 50 % and never be recovery again.