For more information regarding BMS clinical trial participation, please visit www.BMSStudyConnect.com Key Inclusion Criteria: - Eastern Cooperative Oncology Group performance status of 0 or 1 - Histologically confirmed unresectable Stage III or Stage IV melanoma - No prior systemic anticancer therapy for unresectable or metastatic melanoma. Note that prior adjuvant or neoadjuvant melanoma therapy is permitted if it was completed at least 6 weeks prior to date of first dose, and all related adverse events have either returned to baseline or stabilized - Tumor tissue obtained in the metastatic setting or from an unresectable site must be provided for biomarker analyses and sent to the central laboratory. Biopsy should be excisional, incisional punch, or core needle. Fine needle aspirates or other cytology samples are insufficient - Known BRAF V600 mutation status as determined by an FDA-approved test. Patients with either V600 wild-type or V600 mutation-positive melanoma are eligible. Key Exclusion Criteria: - Active brain metastases or leptomeningeal metastases. Patients with treated brain metastases are eligible if there is no evidence of progression on magnetic resonance imaging scan for at least 8 weeks after completion of treatment and within 28 days prior to first dose of study drug administration. There must also be no requirement for high doses of systemic corticosteroids that could result in immunosuppression (>10 mg/day prednisone equivalents) for at least 2 weeks prior to study drug administration - Ocular melanoma - Patients with active, known, or suspected autoimmune disease. Those with vitiligo, type I diabetes mellitus, residual hypothyroidism due to autoimmune condition only requiring hormone replacement, psoriasis not requiring systemic treatment, or conditions not expected to recur in the absence of an external trigger are permitted to enroll.