Ligands are molecules or ions that can bind to a central metal atom to form a complex. They have one or more pairs of electrons that they can donate to the metal, which helps stabilize the complex. Ligands can be classified as either monodentate, which bind through a single atom, or polydentate, which can attach through multiple atoms. In coordination chemistry, ligands play a crucial role in determining the properties of metal complexes, such as their color, reactivity, and solubility. Common examples of ligands include water, ammonia, and chloride ions. Understanding ligands is essential for fields like biochemistry and materials science.