Methionine is an essential sulfur-containing amino acid critical for protein synthesis, methylation reactions via S-adenosylmethionine, and as a precursor for cysteine and taurine. It plays key roles in detoxification, antioxidant defense through glutathione, and lipid metabolism. Naturally occurring in foods like eggs, fish, and nuts, it is used as a dietary supplement and in animal feed. Chemically stable under normal conditions, it decomposes at high temperatures without boiling. As a food compound, it contributes to flavor precursors in some processed foods and is recognized for its role in human nutrition.