 This study is being done to evaluate the impact of moderate-intensity exercise such as walking on quality of life, energy level, endurance and mood in women with metastatic breast cancer. Studies have shown that women with early stage breast cancer who exercise during treatment have more energy, less sleep disturbance, less anxiety and depression, and better strength and endurance than women who do not exercise. These studies have also shown that women who exercised during treatment for early stage breast cancer did not develop injuries or increased fatigue from exercising during chemotherapy and radiation treatments. The investigators are conducting this trial to see if women with metastatic breast cancer experience similar benefits from exercise as women with earlier breast cancer. The investigators also wish to determine whether women with advanced disease are able to exercise safely during their treatment under the supervision of an exercise physiologist. 