Aluminum containers in the microwave oven

I heated up some leftovers tonight after I took them out of the aluminum carry-out container and put them on a paper plate. To my surprise I’ve just noted the legend on top of the lid: “Aluminum containers are microwaveable. Remove lid.” What? I thought metal in the microwave oven was verboten. What’s up with that?

I frequently leave spoons and forks in/on the dishes that I microwave. I’ve never had a problem with it. I know that some metal shapes with lots of edges can arc, so if I were to see that, I’d stop it.

However, I’ve heard some people state that metal in a microwave oven will cause harm to it, and I don’t believe this.

I learned in Home Ec about a technique called shielding where u actually wrap a potatoe for example partly in tin foil to “shield” some of the microwaves.

hahahaha potatoe im an idiot

I’ve accidentally left a fork in the microwave a couple times and was treated a nice arc. Our microwave was a big old monster of an appliance so newer models might behave a little differently.

My microwave actually came new with a removable metal grill-like rack in the bottom. I’m pretty sure it’s “metal safe”.

In high school, we were able to buy Pop-Tarts in the school cafeteria. One day, a friend of mine decided he wanted them hot. He put the Pop-Tarts, aluminum foil and all, in the microwave. The aluminum foil started to glow red, and then POOF! The aluminum foil exploded. Upon opening the microwave, we couldn’t find a single shred of aluminum foil.
My friend said the Pop-Tarts were nice and warm though.

There is nothing wrong with metal in a microwave oven, per se. The whole inside of the oven is made of metal.

The possible problems relate to the fact that metal, at least if it is solid enough, reflects microwaves rather than letting them go through. So if you put a round metal bowl in there, it can reflect the microwaves and concentrate them toward the center of the bowl, just like a reflector around a light bulb can do. Another problem is that separate pieces of metal can develop voltages along their lengths, so a metal fork leaning in a metal bowl may arc at the two points where bowl and fork touch each other. Finally, if metal is quite thin, like a foil or especially like a very thin metal plating on plastic wrap or ceramics or glass, it will attempt to reflect the microwaves by circulating currents through the metal, but will overheat and burn away in the process.