A Study of Amivantamab and mFOLFOX6 or FOLFIRI Versus Cetuximab and mFOLFOX6 or FOLFIRI as First-line Treatment in Participants With KRAS/NRAS and BRAF Wild-type Unresectable or Metastatic Left-sided Colorectal Cancer

Inclusion Criteria: * Have histologically or cytologically confirmed adenocarcinoma of the left-sided colorectal cancer. Participants must have unresectable or metastatic disease * Determined to have Kirsten rat sarcoma viral oncogene (KRAS), neuroblastoma RAS viral oncogene homolog (NRAS), and v-raf murine sarcoma viral oncogene homolog B (BRAF) wild-type (WT) tumor by local and/or central testing (if available) * Must agree to the submission of fresh tumor tissue * Have measurable disease according to RECIST v1.1 * Has not received any prior systemic therapy for unresectable or metastatic colorectal cancer (CRC). Prior adjuvant/neoadjuvant therapy in the non-metastatic disease is permitted. However, the last course of adjuvant or neoadjuvant chemotherapy must have concluded greater than (\>) 12 months prior to CRC recurrence/metastases * Have an eastern cooperative oncology group (ECOG) performance status (PS) of 0 or 1 Exclusion Criteria: * Has medical history of (noninfectious) interstitial lung disease (ILD) /pneumonitis/pulmonary fibrosis or has current ILD/pneumonitis/pulmonary fibrosis, or where suspected ILD/pneumonitis/pulmonary fibrosis cannot be ruled out by imaging at screening * Has known allergies, hypersensitivity, or intolerance to excipients of any of the following: (a) amivantamab or cetuximab, (b) any component of mFOLFOX6 and, (c) any component of FOLFIRI * Has a prior or concurrent second malignancy other than the disease under study or one whose natu…