(1) Conductors. Conductors over a certain thickness, such as copper, silver, aluminum and other metals, can reflect microwaves. In the microwave system, it is often used to transmit microwave energy in the special form of reflection of microwave by conductors. For example, waveguides commonly used in microwave devices are rectangular or round metal tubes, usually made of aluminum or brass. They are like optical fiber to conduct light, which is the path of microwave.

(2) Insulator. In microwave system, insulator has a completely different position from ordinary circuit. The insulator can penetrate microwave, and the microwave power absorbed by it is very small. The interaction between microwave and insulator is like the relationship between light and glass. Glass reflects part of light, but most of it passes through, and only a small part is absorbed. In the microwave system, glass, ceramics, polytetrafluoroethylene, polypropylene plastics and other insulators are used according to different situations. They are often used as the materials of reflectors. Insulator materials can also be used as effective barriers in microwave systems to help prevent dirt from entering certain vital parts.

(3) Media. For microwave, the medium has the properties of absorption, penetration and reflection. Medium is usually used as heating material to absorb microwave energy in varying degrees. This kind of material is also called lossy medium. Especially for foods containing water and fat, they absorb microwave energy to varying degrees and convert it into heat.

(4) Polar and magnetic compounds. The general properties of such materials are very similar to that of media, and they also reflect, absorb and penetrate microwaves. It should be pointed out that since microwave energy has electric and magnetic fields that can affect dielectric materials and polar and magnetic materials, many polar compounds and magnetic materials, like dielectric materials, are also easy to be used as microwave processing materials.