This trial is testing whether a type of psychotherapy called Acceptance and Commitment Therapy (ACT) can help reduce fatigue, interference with activities, mood, and cognition in people with metastatic breast cancer (MBC). ACT includes mindfulness exercises (e.g., meditations, performing activities with greater awareness), identifying personal values (e.g., family, work), and engaging in activities consistent with these values. A total of 250 patients will be randomly assigned to either the ACT intervention or an education/support condition. Patients in both conditions will participate in six weekly 50-minute telephone sessions. Outcomes will be assessed at baseline, 2 weeks post