Cofactors are non-protein chemical compounds that assist enzymes in catalyzing biochemical reactions. They can be metal ions, like zinc or magnesium, or organic molecules known as coenzymes, such as NAD+ or vitamin B12. Cofactors help enzymes achieve their active form, enabling them to interact with substrates effectively. In many cases, cofactors are essential for enzyme activity, meaning that without them, the enzyme would be inactive. They can be tightly bound to the enzyme or loosely associated, and their presence can significantly influence the rate and efficiency of metabolic processes in living organisms.