1. Carbon (C): The backbone of all organic molecules, including macromolecules, is made of carbon. Carbon's ability to form four bonds allows for the creation of complex and diverse structures.

2. Hydrogen (H): Hydrogen is found in almost all macromolecules and is a key component of many functional groups.

3. Oxygen (O): Oxygen is involved in many important functions within macromolecules, including the formation of functional groups and the creation of water during reactions.

While these are the three most common elements, other elements like nitrogen, phosphorus, and sulfur can also be present in various macromolecules.