WATCH: Here’s What Really Happens When You Put Metal In The Microwave

Your mother probably told you that you should never ever ever put metal in the microwave. But is that old adage really true?

For the answer, check out the video above. It explains what you can — and what you definitely should not — put in the microwave.

“If it’s got sharp edges or if it’s thin it’s going to cause some trouble,” Dr. Louis Bloomfield, a professor of physics at the University of Virginia, told The Huffington Post. “The sharp edges are likely to shoot sparks, and if it’s thin, it’s likely to get very hot.”

So forks, twist ties, the handles on takeout containers are among the likeliest items to trigger sparks.

Said Bloomfield, “A spoon is safer.”

Of course, it’s best to keep all metal out of the microwave. Mum was right.