A Study With Combinations of Anti-LAG-3 and Anti-PD-1 Antibodies in Adult Participants With Advanced or Metastatic Melanoma (Harmony Head-to-Head)

Key Who May Qualify: 1. Participants with diagnosed by tissue sample (biopsy-confirmed) unresectable stage III and stage IV (metastatic) melanoma per American Joint Committee on Cancer (AJCC), eighth revised edition. 2. Participants must not have received previous cancer treatment that works throughout the body (like chemotherapy) for unresectable or metastatic melanoma as described in the protocol. 3. tumors that can be measured on scans version 1.1. 4. Eastern Cooperative Oncology Group (ECOG) performance status (PS) ≤1 5. Adequate bone marrow, hepatic, and kidney function 6. Known B-Rapidly Accelerated Fibrosarcoma protein (BRAF) V600 mutation status or submitted sample for BRAF V600 mutation assessment as described in the protocol Key Who Should NOT Join This Trial: Medical Conditions: 1. Uveal, acral or mucosal melanoma. 2. Ongoing or recent (within 2 years) evidence of an autoimmune conditions (where your immune system attacks your own body) that required systemic treatment with immunosuppressive agents as described in the protocol. 3. Uncontrolled infection with human weakened immune system virus (HIV), hepatitis B (HBV), or hepatitis C virus (HCV) infection; or diagnosis of weakened immune system that is related to, or results in chronic infection. Mild cancer-related weakened immune system (such as weakened immune system treated with gamma globulin and without chronic or recurrent infection) is allowed. Prior/Concomitant Therapy: 4. Prior immune checkpoint inhibitor therapy other than anti-PD1/PD-L1 as described in the protocol 5. Systemic immune suppression as described in the protocol. Other Comorbidities: 6. Participants with a history of myocarditis. 7. Troponin T (TnT) or troponin I (TnI) \>2x institutional upper limit of normal (ULN). 8. Active or untreated brain metastases or spinal cord compression as described in the protocol. Note: Other protocol-defined Inclusion/ Exclusion Criteria apply. Always talk to your doctor about whether this trial is right for you.