RATIONALE: Sorafenib may stop the growth of tumor cells by blocking blood flow to the tumor and by blocking some of the enzymes needed for cell growth. Estrogen can cause the growth of breast cancer cells. Aromatase inhibition therapy using letrozole, anastrozole, or exemestane may fight breast cancer by lowering the amount of estrogen the body makes. It is not yet known whether sorafenib is more effective than a placebo when given together with letrozole, anastrozole, or exemestane in treating metastatic breast cancer.