The skeleton is constantly being remodelled through the simultaneous resorption of bone and formation of new bone. Significant effects on bone metabolism are produced due to cancer treatment especially of breast and prostate origin, even in the absence of bone metastases. These pathological changes are known as cancer treatment-induced bone loss. Bone mass loss and osteoporosis may cause an increased risk of fractures due to a reduction in bone volume and microarchitectural deterioration. On the other hand, the skeleton is both the most common organ affected by metastatic cancer and the site that produces the greatest morbidity for patients. Recent advances in our understanding of bone biology and the pathways by which cancer metastasizes and spreads to bone have contributed to the development of several important new drugs targeting these processes. This article summarizes our current knowledge and recommendations to advanced biology of metastasis, focusing on breast and prostate cancer.