Payload delivery methods: phishing (email attachment or link), physical USB drop, watering hole (compromised website), supply chain (compromised update), exploitation (direct RCE).
Email phishing is by far the most common initial access vector in real attacks. Payload delivery is Kill Chain stage 3 (Delivery). msfvenom generates custom payloads for specific architectures and formats (PE, macro, HTA, shellcode). AV evasion is critical at this stage.