The main purpose of this study is to evaluate the safety and tolerability of the study drug LY3849891 in participants with metabolic dysfunction-associated steatotic liver disease (MASLD) who have the patatin-like phospholipase domain-containing protein 3 (PNPLA3) I148M genotype. Blood tests and magnetic resonance imaging of the liver will be performed to determine the effects of LY3849891 on MASLD and assessment of resolution of liver fibroinflammation. Blood tests will also determine how long it takes the body to eliminate LY3849891. This is a 2-part study and may last up to 32 weeks for each participant and may include 12 visits in parts A and B.