Microwaves heat food by creating electromagnetic fields that excite polar molecules (like water) causing them to vibrate and generate heat. But when you put metal in a microwave, especially thin pieces like aluminum foil, things get wild. That’s because metal reflects microwaves. And when the foil has sharp edges or folds, the electric field gets extremely concentrated at those points. This intense energy can rip electrons off nearby air molecules, ionizing the gas and creating plasma: a glowing