• DESs are emerging as green alternatives to toxic organic solvents and ionic liquids in critical metal metallurgy, offering low toxicity, biodegradability, and cost-effectiveness.
• The review systematically covers DES classification, formation mechanisms, preparation methods, characterization technologies, and tunable physicochemical properties.
• DES-based separation and purification processes show significant promise for improving efficiency and sustainability in the recovery of critical metals.
• Future research must address challenges such as viscosity, recyclability, and scale-up to fully realize industrial applications of DESs in metallurgy.