Breast cancer is a disease that has plagued many women globally. The rapid rise in the incidence rate has prompted the rigorous search to understand its etiology and find better management strategies for this disease. Metallothionein (MT) belongs to a family of metal-binding proteins where dysregulated expression of this protein has been observed in invasive breast ductal carcinomas. Since its discovery in equine kidney, functions of MT have extended beyond the initial role of heavy metal detoxification to promoting tumorigenesis. MT, which was reported to be highly expressed in many tumors including breast cancers, is known to regulate key processes such as cell proliferation, apoptosis and even chemoresistance. In this patent review, we shall evaluate the roles of 10 functional isoforms of MT in breast neoplasia and discuss the utility of MT isoforms as biomarkers for prognosis. Strategies targeting MT for treatment could provide alternatives to overcome this dreaded disease which has claimed the lives of many women.