If we're talking rust/resto work on an old car for which there is no OEM repair procedure, it would be best to research the types of adhesives that are available and applicable to the job at hand to see if they are a viable option. If we're talking collision repair on a vehicle for which there is an OEM repair procedure, you do what the procedure says, period. If it says weld, then weld. If it says bond, then bond. Anyone who deviates from that is a hack and an effing moron.