The purpose of this study is to compare pembrolizumab (MK-3475) in combination with sacituzumab govitecan with pembrolizumab alone with respect to progression-free survival (PFS) and overall survival (OS) per Response Evaluation Criteria in Solid Tumors Version 1.1 (RECIST 1.1) as assessed by blinded independent central review (BICR) among adults with metastatic non-small cell lung cancer (NSCLC) with programmed cell death ligand 1 (PD-L1) tumor proportion score (TPS) ≥50%).