What happens when you accidentally microwave a metal fork, and then eat the food it was in? — RH, Seattle
Both the fork and the food are almost certainly safe. While the microwave oven is operating, electric current will flow through the fork and electric charge will accumulate momentarily on the tips of the fork’s tines. However, most forks are thick enough to handle the current without becoming noticeably hot and have tines that are dull enough to accumulate the charge without sparking. The end result is that the fork doesn’t do much while the oven is operating; it reflects the microwaves and therefore alters the cooking pattern slightly, but you probably won’t be able to tell. Once the cooking is over, the fork is just as it was before you put it in the oven and the food is basically just microwaved food.
If a fork has particularly sharp tines, however, then you should be careful not to put in the microwave oven. Sharp metal objects can and do spark in the microwave oven. Those sparks are probably more of a fire hazard than a food safety hazard—they can ignite the food or its container and start a fire.