The main purpose of this study is to find out whether the study drug, LY4050784, is safe, tolerable and effective in participants alone or in combination with other anticancer agents. In addition, with locally advanced or metastatic solid tumors with a BRG1 (Brahma-related gene 1, also known as SMARCA4) alteration who have previously received, do not qualify for, or are refusing standard of care treatments, or there is no standard therapy available for the disease. The study is conducted in two parts - phase Ia (dose-escalation) and phase Ib (dose-optimization, dose-expansion). The study will last up to approximately 4 years.