This clinical trial evaluates the combination of olomorasib and pembrolizumab as a first-line treatment for patients with advanced or metastatic non-small cell lung cancer (NSCLC) that has a Kirsten Rat Sarcoma Virus (KRAS) G12C mutation and a programmed death-ligand (PD-L1) score between 1% and 49%. The main goal of the study is to determine how long patients live without their cancer worsening after starting treatment, also known as progression-free survival (PFS). Additional goals include evaluating how many patients experience tumor shrinkage or disappearance, how long responses to treatment last, overall survival, and the safety and side effects of the treatment combination. Furthermore, how well the treatment works in patients whose cancer has spread to the brain, outcomes in patients with a lower Eastern Cooperative Oncology Group performance status (ECOG), and whether certain tumor or blood-based biomarkers are associated with treatment response or side effects, if enough patient data is available for analysis.