What-happens-when-you-warm-up-food-in-the-microwave, placing plastic food containers in the microwave may be harmful to your health. some containers are okay and others are not. it's important to understand why plastic food containers are a problem and how to avoid the dangers.. The microwave oven is one of the great inventions of the 20th century -- you can find them in millions of homes and offices around the world. at one time or another, we've all been told not to use metal products, especially aluminum foil, when cooking with a microwave oven.stories of incredible explosions and fires usually surround these ominous warnings.