This is an efficacy and safety study to assess pembrolizumab (MK-3475/SCH 900475) compared to standard of care (SOC) platinum-based chemotherapies in the treatment of participants with previously untreated stage IV, programmed cell death ligand 1 (PD-L1) strong expressing Non-Small Cell Lung Cancer (NSCLC). The primary hypothesis of this study is that participants with PD-L1 strong NSCLC will have a longer Progression Free Survival (PFS), as assessed by Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST 1.1) when treated with pembrolizumab than when treated with SOC platinum-based chemotherapies.