YouTube creators The Slow Mo Guys decided to find out what happens when you put an airbag in a microwave. You can probably guess what happened. Don't try this at home!
In 1945, the microwave oven was accidentally discoverd after an engineer discovered that the radar waves he was experimenting with were melting the candy bar in his pocket. The first microwave oven was sold in 1946 and called the Radarange.
Metals, when placed in a working microwave, act as an antenna in which the electricity from the microwave can travel to and create a spark of plasma. In this case, the spark triggers the activiation of the airbag inside the microwave.