Stellar metallicity refers to the abundance of elements heavier than helium in a star's composition. This can provide important information about the star's formation history, age, and evolutionary stage. Studying stellar metallicity can help astronomers understand the overall chemical evolution of galaxies and the universe, as well as the formation of planetary systems around stars. Techniques used to determine stellar metallicity include spectroscopy, which analyzes the absorption lines in a star's spectrum to measure the relative abundances of different elements.