The purpose of this study is to evaluate two study medicines (encorafenib plus cetuximab) taken alone or together with standard chemotherapy for the potential treatment of colorectal cancer that: * has spread to other parts of the body (metastatic); * has a certain type of abnormal gene called "BRAF"; and * has not received prior treatment. Participants in this study will receive one of the following study treatments: * Encorafenib plus cetuximab: These participants will receive encorafenib by mouth at home every day and cetuximab once every two weeks by intravenous (IV) infusion (an injection into the vein) at the study clinic. * Encorafenib plus cetuximab with chemotherapy: These participants will receive encorafenib and cetuximab in the way described in the bullet above. Additionally, they will receive standard chemotherapy by IV infusion and oral treatment at home. * Chemotherapy alone: These participants will receive chemotherapy, the standard treatment for this condition, by IV infusion at the study clinics and oral treatment at home. This study is currently enrolling participants who will receive either encorafenib plus cetuximab with chemotherapy or chemotherapy alone. The study team will monitor how each participant responds to the study treatment for up to about 3 years.