Why does the wire weld when I touch the metal?

A great many older home mig welders were produced with a live torch, ie. the manufacturer had saved the cost of the contactor, the high current electromechanical relay that switches the welding current on or off in response to the torch trigger...

It was inevitable some manufacturers would replace the rectifiers and contactor with thyristors (SCRs) and obtain both functions from a single modification.

The trigger switch controls the wire motor and the contactor so if the wire motor is working ok it is unlikely the fault is there and if your welder has a contactor it could be stuck or a wiring fault has caused the coil to be permanently energised or if your welder uses the solid state version, either one or more of the thyristors have failed or a circuit fault has caused the supply to the gate to be permanent causing them to be permanently switched on.

The tip of the welder may need cleaned out, your feed speed might need slowed down, check the polarity is it straight or reverse?

Assuming the Trig Stuk is a message on a display tells me you have a later model welder. Try downloading the manual from Miller. Or if you're adventurous look at the trigger and see if it is stuck, take it apart, clear any debris blocking the trigger contact (preventing it from opening after the trigger is released). Check for cut or twisted wires and see if they are connected at the wire feed motor or has one come off? Is a piece of weld wire touching the motor feed connections?

I have a clarke 85en no gas welder. the gun on this particular welder is always live the trigger only feeds the wire

Check to make sure the contact is not touching the nozzle of the mig welder. This would definitely short it out!

does this unit have a high side and a low side if it does plug it into the low side and try it.

Sounds like the trigger is getting worn out.

try dipping the tip in some grease be fore welding or increase your wire speed a touch and see if that helps

the problem is your project is not grounded, attach the grounding cable from your welder to your project your welding.