Inclusion Criteria:

* Participant must have histologically or cytologically confirmed NSCLC and must have metastatic NSCLC at the time of enrollment
* Participant must have at least 1 measurable lesion, according to RECIST v1.1, that has not been previously irradiated
* May have brain metastases only if previously definitively treated, and participant is clinically stable and asymptomatic for >2 weeks and is off or receiving low-dose corticosteroid treatment (<=10 mg prednisone or equivalent) for at least 2 weeks prior to start of study treatment
* May have a prior malignancy (other than the disease under study) if the natural history or treatment is unlikely to interfere with any study endpoints of safety or the efficacy of the study treatment(s)
* Have an ECOG performance status of 0 or 1

Exclusion Criteria:

* For Phase 2 only: Participant has known oncogenic driver mutations (EGFR, MET, HER2, ALK, ROS1, NTRK, BRAF, RET, or KRAS) as detected by local testing or by central ctDNA testing
* Participant has received radiotherapy for palliative purposes less than 14 days prior to the first dose of study treatment
* Participant has: a.(Or has a history of) leptomeningeal disease (carcinomatous meningitis); b. Spinal cord compression not definitively treated with surgery or radiation.
* Medical history of (non-infectious) ILD/pneumonitis, or has current ILD/pneumonitis, or where suspected ILD/pneumonitis cannot be ruled out by imaging at screening- Participant has history of any significant drug allergy (such as anaphylaxis, hepatotoxicity, or immune-mediated thrombocytopenia or anemia) or has known allergies, hypersensitivity, or intolerance to: a. amivantamab or amivantamab excipients (refer to the amivantamab IB); b.docetaxel, docetaxel excipients or to other drugs formulated with polysorbate and paclitaxel