The very nature of the food itself determines much about the way it should be cooked. Meat can be a tricky item to cook in the microwave. If the piece of meat you're cooking has even fat distribution and no bones, the meat should cook fairly evenly. If it has fat pockets in certain areas or a bone running through the meat, you'll want to turn the piece of meat frequently during the cooking process. Meat is also one of the more dense foods you'll cook in a microwave.
Dense foods require longer cooking times than light foods such as bread or brownies.
In fact, these lighter items require such short heating times that cooks often overcook them and end up sucking every drop of moisture from an innocent piece of bread. Adding a bowl of water beside a piece of bread when you heat it can help to alleviate this risk. Some meats, such as fish and poultry, have a high moisture content and will therefore cook more quickly and require less turning than drier items. Foods with very low moisture content should have water added to them while you cook them in the microwave. The ideal food to cook in a microwave will have small, moist, even pieces that are all the same size.