This study is to assess the pharmacokinetics (PK) and safety of SC pembrolizumab formulated with berahyaluronidase alfa (MK-3475A) versus (vs) intravenous (IV) pembrolizumab (MK-3475), administered with chemotherapy in first line treatment of adult participants with metastatic non-small cell lung cancer. The primary hypotheses of this study are pembrolizumab formulated with berahyaluronidase alfa subcutaneous (SC) is noninferior to pembrolizumab IV with respect to PK parameters.