Tied correctly, a simple rope halter can be an invaluable groundwork training aid. I think of a rope halter as a training aid. It allows you to apply enough pressure on a horse’s face to get his attention and/or gain control.
It is a far superior tool, in my opinion, and experience, than using a stud chain on a horse for control because you can finesse the pressure with a rope halter. A stud chain will put constant pressure on the horse - you can make the pressure worse but you can never totally release it.