Which component is referred to as the main part of a weapon, which can be constructed from steel, alloy, or polymer?

The main part of a weapon is known as the frame. This component serves as the foundational structure that houses the other essential parts of a firearm, facilitating the operation and stability of the weapon during use. The frame is typically constructed from materials such as steel, alloy, or polymer, making it durable and resilient to the forces experienced when firing the weapon. Its design and construction are crucial for maintaining the firearm's integrity and performance over time.

In contrast, the safety/decocker, sights, and trigger guard are all important components of a firearm but serve specific functions. The safety/decocker is a mechanism designed to prevent accidental discharge, while sights assist in aiming the weapon, and the trigger guard provides protection for the trigger to prevent unintended firing. Although these components are integral to the firearm's operation, they do not serve as the primary structural element like the frame does.