There are three ways that objects can react to microwave energy within a microwave cavity:

1. 1. They can absorb microwave enengy. This is the case with all polar molecules (substances with positive and negative ionic poles). Examples include water, alcohols and biological specimens. Objects which absorb microwave energy will get hot as a result. The total amount of microwave absorbing material within the miaowave cavity is called the “load.”

2. 2. They can reflect microwaves. This is the case with metals. The function of the medal walls which make up a microwave cavity is to keep the microwave energy within the cavity. The metal walls themselves will not get hot.

3. 3. They can be “microwave-transparent.” This is the case with many non-polar molecules, such as paraffin and many plastics. Objects which ane microwave transpanent will heet very poorly in a microwave.