Which tool would you use to ensure a secure connection when joining metal wires?

Using a soldering iron is appropriate for ensuring a secure connection when joining metal wires because it allows for the melting of solder, which is a fusible metal alloy. When wiring is joined through soldering, the solder fills the gaps between the wire connections and creates a strong, electrically conductive, and mechanical bond. This method is particularly effective for ensuring that the joint can withstand physical movement and environmental factors, which is essential in electrical applications.

In contrast, while tools like wire strippers, crimping tools, and insulation testers have their respective functions, they do not focus on creating a secure and lasting bond between wires. Wire strippers are used to remove insulation from wires to expose the metal conductors, crimping tools are designed to join wires with metal connectors through deformation, and insulation testers are used to check the integrity of insulation on wires rather than to join them. Each of these tools serves a specific purpose that does not involve soldering, which is crucial for creating robust electrical connections.