A Study of Subcutaneous Nivolumab + Relatlimab Fixed-dose Combination (FDC) in Previously Untreated Metastatic or Unresectable Melanoma

Inclusion Criteria

* Participants must have an Eastern Cooperative Oncology Group (ECOG) performance status of ≤ 1/Lansky Performance Score ≥ 80% for adolescents (≥ 12 to \< 18 years of age).
* Participants must have histologically confirmed Stage III (unresectable) or Stage IV (metastatic) melanoma, per the American Joint Committee for Cancer (AJCC) staging system.
* Participants must have measurable disease by computed tomography (CT) or magnetic resonance imaging (MRI) per Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST v1.1).
* Participants must be ≥ 12 years of age. Participants who are ≥ 12 years of age and \< 18 years of age (adolescents) must weigh ≥ 40 kg at the time of signing the informed consent (assent).
* Participants must have histologically confirmed Stage III (unresectable) or Stage IV (metastatic) melanoma, per the AJCC staging system (8th edition).

Exclusion Criteria

* Participants must not have ocular melanoma.
* Participants must not have a history of myocarditis, regardless of etiology.
* Participants must not have a condition requiring systemic treatment with either corticosteroids (\>10 milligrams \[mg\] daily prednisone equivalent) or other immunosuppressive medications within 14 days of start of study treatment. Inhaled or topical steroids, and adrenal replacement steroid doses \>10 mg daily prednisone equivalent, are permitted in the absence of active autoimmune disease.
* Other protocol-defined Inclusion/Exclusion criteria apply.