A waveguide cover's main job is to transmit microwave radiation. It prevents steam and food particles from interacting with the electrical components within the microwave oven. ... The main use is to prevent splashes and bits of food from getting into the cavity of the microwave.

Can I use microwave without waveguide?

While it may appear you can continue to use your microwave oven without the waveguide cover, we highly recommend you do not. Continued use could cause a short and/or corrosion to the unit's magnetron and internal circuits creating a safety hazard as well as eventually rendering the unit beyond repair.

Why do we need waveguides?

Waveguides are used to direct and propagate Electromagnetic waves from one point to another. They are generally used to transmit high frequency waves such as Microwaves, Radio waves, Infrared waves etc. For low frequency waves which are less than 1 MHz, parallel transmission lines or co-axial cables are used.