Even the most basic microwave oven is safe to use, so long as the user follows the general principles of microwave safety. Using the right sort of dishware and keeping most metals out of the microwave allow safe cooking of food.
Food that is in heatproof glass, ceramic, an oven cooking bag, or any other container marked safe for the microwave is safe to prepare in this type of oven. Wax paper and parchment paper are safe as well. However, plastic cold storage containers, metal pans, anything lined with foam, and brown paper bags are not microwave-safe. Metal twist ties and aluminum foil should also stay out of the microwave. When preparing frozen food in the microwave, it's important to leave the food frozen until ready to microwave, as thawing gives bacteria the chance to multiply.