This study is designed to test how well once-weekly MET097 (an ultra-long-acting GLP-1 receptor agonist) works to treat adults with obesity or overweight and type 2 diabetes mellitus (T2DM) compared to placebo. MET097 or placebo will be administered to individuals via subcutaneous injection once weekly for 28 weeks. If an individual is randomly assigned to MET097 they will receive one of four different dose regimens.