The main purpose of this study is to find out the most suitable dose (recommended phase 2 combination dose \[RP2CD\]) of amivantamab and olomorasib combination therapy and to assess how well the combination slows down or prevents the growth of tumors in participants with KRAS G12C mutant metastatic non-small cell lung cancer (NSCLC: the most common type of lung cancer; metastatic: has spread to other parts of the body; KRAS G12C mutant: mutation \[change\] in the kirsten rat sarcoma viral oncogene homolog \[KRAS\] gene in tumor cells in which glycine \[G\] at position 12 is replaced with cystine \[C\]).