Is a microwave example of a transmission media?

In short: no. A transmission media is a material substance (solid, liquid or gas) through which energy waves can travel. For example, the transmission medium for sound received by the ears is usually air, but solids and liquids may also act as transmission media for sound.

It can also refer to the technical device which employs the material substance to transmit or guide the waves. Thus an optical fiber or a copper cable can be referred to as a transmission medium.

Microwaves are a form of electromagnetic energy, similar to radio waves. Whatever microwaves travel through (i.e.: the air) is the transmission media.