The main purpose of this study is to learn about the side effects of LY3437943 when given to participants with type 2 diabetes. Blood tests will be performed to investigate how the body processes the study drug and how the study drug affects the body. Each enrolled participant will receive injections of LY3437943, dulaglutide, or placebo given just under the skin. For each participant, the study will last up to about 5 months and will include 16 visits to the study center.

Inclusion Criteria:

• Have T2DM for at least 3 months before screening and are without advanced known possible complications of diabetes mellitus
• Have a glycated hemoglobin (HbA1c) value at lead-in and screening of ≥7.0% and ≤10.5% and treated with diet and exercise alone or a stable dose of metformin for at least 3 months prior to screening
• Have had a stable body weight for the 3 months prior to randomization (<5% body weight change)
• Have a body mass index of 23 to 50 kilograms per square meter (kg/m²), inclusive
• Male participants agree to use an effective method of contraception for the duration of the study plus 90 days, which corresponds to 4 months after the last investigational product dose
• Women not of childbearing potential may participate and include those who are: infertile due to surgical sterilization (hysterectomy, bilateral oophorectomy, or tubal ligation), congenital anomaly such as mullerian agenesis; or those who are postmenopausal

Exclusion Criteria:

• Have type 1 diabetes mellitus or latent autoimmune diabetes in adults
• Have uncontrolled diabetes, defined as an episode of ketoacidosis or hyperosmolar state requiring hospitalization in the 6 months prior to screening
• Have a known clinically significant gastric emptying abnormality
• Have had an episode of severe hypoglycemia
• Have a history of acute or chronic pancreatitis or fasting serum triglyceride level of >500 milligrams per deciliter (mg/dL) at screening and/or Day-2. If participant is on lipid-lowering therapies, doses must be stable for 30 days prior to screening
• Have known liver disease, obvious clinical signs or symptoms of liver disease, acute or chronic hepatitis, or have elevations in aminotransferases (alanine aminotransferase [ALT] and aspartate aminotransferase [AST]) greater than 3X upper limit of normal (ULN) at screening and/or Day -2