Slag produced as a byproduct in industrial processes, contains considerable metals contents, which need to be recovered to avoid environmental contamination. In present review, the types, applications, recovery of metals from slag and their hazardous effects have been discussed. Gravimetric, magnetic, floatation, pyrometallurgical and hydrometallurgical treatments are discussed for processing of charge chrome, steel, copper smelter, brass smelter, tin, incineration, ferrochrome and silico-manganese slags for the extraction of various metal ions (Mg, Cu, Zn, Pb, Cd, Ni, Co, Mn, Fe, As, Cr, Al, Nb, Ag, Au, Nb, Ta, Cu, Co, Ni, Fe, V, Cr). The possibility of biometallurgical processing of slags is also evaluated. Merits and demerits of extraction and purification techniques are highlighted with possible suggestions and possibility of integrated leaching techniques is also discussed.