Additional Study Information: This study is being done to see how safe an investigational drug, LY3484356 is and how well it will work to help people with estrogen receptor-positive (ER+), HER2 negative (HER2-) locally advanced or metastatic breast cancer previously treated with endocrine therapy. The main reason for you to take part in this study is not to treat you for your condition but to help in answering the following research question: How LY3484356 compares to the investigator's choice of either fulvestrant or exemestane for the treatment of ER+, HER2- breast cancer?