What do we call a chemical substance that is involved in metabolic processes?

A chemical substance that is involved in metabolic processes is referred to as a metabolite. Metabolites are the intermediate or end products of metabolism, which can include small molecules such as amino acids, sugar molecules, and more complex compounds. They play essential roles in the body's biochemical reactions and processes, serving as substrates for enzymatic reactions, byproducts of metabolic pathways, or necessary components for energy production.

In contrast, enzymes are biological catalysts that facilitate these metabolic reactions but are not themselves consumed in the process. Substrates are the specific reactants that enzymes act upon during a biochemical reaction, while reactants are the starting materials in any chemical reaction that may or may not be involved in metabolic pathways. Thus, while all these terms relate to metabolism, metabolite is the most accurate term for substances involved in the metabolic processes themselves.