How to Train the Hard-to-Bridle Horse

Change the Bit

If all of that checks out, then consider trying a change of bit. Many horses prefer a copper mouthpiece over stainless steel. (Avoid using older, cheap nickel bits—horses can actually have an unpleasant allergic reaction to them). While the common wisdom is that thicker bits are milder, horses with smaller mouths may need a thinner bit. Horses with low palates should not be ridden in single-jointed bits.

Remove the Noseband or Browband

All of this should remove the negative connotations associated with bridling. The next thing to consider is removing the noseband if you are not using any kind of corrective noseband or tie-down. This makes putting the bridle on easier and may help.

Then, get some molasses or unsweetened apple sauce and smear it on the bit. After a few times of this, most horses will take the bit much more readily. 

Always bridle slowly and carefully and avoid, as much as possible, touching the horse's ears. Many horses hate having their ears touched, and a horse that has had ear mites in the past can have real problems with it.

For horses that are particularly ear shy, it might be worth removing the browband, at least temporarily. Always reward the horse when it lets you bridle it without any hassle.

Don't Punish the Horse

Punishing a horse for refusing to be bridled is counterproductive. Although very occasionally a horse may refuse because it is being dominant or lazy, the vast majority of difficult-to-bridle horses were either poorly trained in the first place, or are trying to tell you something, or are fed up with the way you are putting the bridle on. Fixing this particular problem requires a lot of positive reinforcement and the building of pleasant associations.