Sodium metabisulfite is primarily used as a food preservative, particularly in the brewing and winemaking industries to inhibit the growth of bacteria, yeasts, and fungi. It is also used as a bleach and reducing agent in the textile and pulp industries, as a disinfectant in the medical and sanitation industries, and as a water treatment chemical to remove chlorine and heavy metals. Additionally, it is used as an antioxidant and preservative in the pharmaceutical industry and as a reagent in chemical laboratories.