Researchers want to know if V940 (the study treatment) given with pembrolizumab and chemotherapy can treat metastatic treatment-naive squamous non-small cell lung cancer (NSCLC). V940 is designed to help a person's immune system attack their specific cancer. The goal of this study is to learn if people who receive V940 with pembrolizumab and chemotherapy live longer overall and without the cancer growing or spreading compared to people who receive placebo with pembrolizumab and chemotherapy. A placebo looks like the study treatment but has no study treatment in it. Using a placebo helps researchers better understand the effects of the study treatment.