I had a Thoroughbred mare that learned that anytime she pulled back the halter would break. I had always used either a nylon or leather halter, and after the first few times, I went and got a standard rope halter and tied her with a quick release tie to make sure I could untie it if I had to, and I tied her up like normal to tack her up, and when she pulled back, she wasn't able to break anything, as she was tied to a metal tie rail cemented into the ground. After that she stopped trying to pull back. I would not use that method on a horse that is truly scared to be tied though. I felt comfortable doing it with her only because her entire reason for pulling back was because she could, and she was able to run home. Not because she was actually scared. If she's scared, I would start by just looping the lead rope over the rail 3 times, so its tight enough that she'll feel pressure when she pulls back, but it will end up coming undone quick enough if she's that scared, and just work with her, give her treats or whatever as long as she's good, and work your way up to actually tying the rope.