I want to hook up some spot lights on the front brush guard. Problem is when I check the line it has 12v constantly.

 

The better way to install the wiring would be to utilize a relay that would be connected to a source controlled by the ign switch.That power from the ign controlled wire could have a toggle switch or rocker sw controlling the relay You can't use a standard relay, it must have a diode or resistor in the relay control side to prevent voltage spikes in the electrical system when the relay coil is denergized. Those spikes can cause unbelievable problems to the vehicle electronics.
A fused wire from the fuse panel to the number 30 on the relay would provide the power for the lights and #87 on the relay would go to the lights themselves.