Is it really dangerous to put metal in the microwave?

Who among us hasn't had the impulse to stick a can of SpaghettiOs in the microwave and see if the whole thing will, maybe like, you know...blow up? Or at least black out every household in the neighborhood? Well, while the occasional spoon left in your microwaving coffee cup won't necessarily win you a Darwin Award, this little rogue science experiment is still not without consequence. The problem has to do with a phenomenon called "arcing." Without getting all Mr. Science on you, it seems microwaves electrically charge the air between a metallic object and the metal contained in the oven walls. This ionized air produces an electric current like a small bolt of lightning that can spark. Sparking in the microwave is more likely when metal with sharp edges, such as forks or even crinkled aluminum foil, is left inside. And the arcing effect can actually melt or burn thin metal layers like those found in mugs with metal trim. Thus, the FDA recommends that you don't use metal and aluminum foil in a microwave, as they can damage the oven and also cause your food to cook unevenly. And while you're exercising caution, don't forget that just boiling water in a microwave can be dangerous as well.