This study is researching an experimental drug called fianlimab (also known as REGN3767), combined with another medication called cemiplimab (also known as REGN2810), called study drugs. The study is focused on patients with a type of skin cancer known as melanoma. The aim of the study is to see how safe and effective the combination of fianlimab and cemiplimab is in treating melanoma, in comparison with the combination of two medications, relatlimab and nivolumab, commercialized under the brand name Opdualag™ and approved for the treatment of melanoma in adults and children. The study is looking at several other research questions, including: * What side effects may happen from taking the study drugs. * How much study drug is in the blood at different times. * Whether the body makes antibodies against the study drugs (which could make the drug less effective or could lead to side effects)