The prefix "macro" means large, so they are large molecules, composed of hundreds, thousands, or even more atoms. Most of these important for our biological functions are organic, meaning that they contain many carbons and hydrogens, and usually with oxygens as well.
The four main types of macromolecules present in all living things: proteins (composed of amino acids), carbohydrates, lipids (fats), and nucleic acids. They are all organic, thus contain carbon and hydrogen.