What Can You Not Put in a Microwave Oven?

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Updated August 18, 2022

If you have been experimenting with the joys of microwave cooking, you may wonder what you cannot put in a microwave oven. Even the best microwave ovens place certain restrictions on what can and cannot be placed inside the microwave cavity. Keep reading to find out more information.


  • Microwaves are great to cook a wide variety of foods, but not every packaging material can be placed inside the cavity.
  • Avoid metal of all kinds, including containers with metal handles, aluminum foil, metal lids, and more.
  • You should also avoid certain plastics, such as those with BPA, and Styrofoam.

How Does a Microwave Work?

Before you learn what can and cannot be placed inside a microwave, it can be helpful to get a simple primer on how a microwave works. These ovens use a component called a magnetron that releases radio waves in the form of heated electrons that are absorbed by some materials, including food items. This is why microwaves tend to cook ingredients from the inside out. Not all types of materials can absorb these electromagnetic waves, thus the below list. Placement will not impact efficacy, but knowing how to place a microwave oven could impact the overall flow and appearance of your kitchen.

What Cannot be Placed in Microwave?

Several materials should not be placed inside of a microwave during use for a variety of reasons.

Insider Tip

Look for the microwave-safe label on any container you are thinking of placing inside of the cavity. You can also check the packaging.


This is the prime offender. Metal should never be placed inside of a microwave, as metal does not absorb microwaves. At best, metal will shield and protect the food from said radio waves, so they won’t get cooked. At worst, metal will interact with the electrical components of a microwave, causing sparks and even fires in the process. Do not even place a little bit of metal in a microwave during use. This includes flecks of aluminum foil, metal handles, and just about anything else. If your microwave already includes a pre-existing metal rack, which is a cooking accessory, that will be fine, as these are designed to avoid sparks and fires. Feel free to place metal in a conventional oven.


Styrofoam is a no-no, as it can actually melt and release harmful chemicals into your food. This includes Styrofoam cups, plates, and containers of all kinds. If you have a cup of matzah ball soup, for instance, and you just learned how to Kasher a microwave, be sure that the soup is not stored in Styrofoam. Otherwise, you’ll have to clean your microwave with steam once more to Kasher it again.

Certain Plastics

Certain plastics should not be placed in a microwave, such as those that include BPA. The wrong plastics can release harmful chemicals as the microwave cooks, which are not exactly fun to ingest. Stick to a microwave-safe container to cook hot peppers, popcorn, or just about anything else. Check ahead of time, as some plastic containers are fine.


Is aluminum foil safe to put in the microwave?

Absolutely not. Aluminum foil can spark and catch fire if placed in a microwave. If you have frozen meats wrapped in foil, remove the foil ahead of time. Also, be sure to check for any metal in Chinese take-out containers.

Can you boil water in the microwave and should you?

Sure, you can boil water in a microwave as it can save time when preparing tea or even hard-boiled eggs. Just make sure you use a microwave-safe container.

Can you microwave paper towels?

You can microwave paper towels, but avoid certain kinds of plastic wrap.

STAT: A microwave oven consumes about 75% less energy in performing a similar task when compared to a conventional oven. (source)

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