do work on getting him to lower his head, like Natisha says. this can be one of the things you do to bond. and, it helps to also get the horse to bend in toward you, not just lowering the head, when you start bridling.
so, you put you hand up over his poll (don't put your whole arm up there, or you could get a dislocated shoulder if he pops his head up). ask for lower. you can have the other hand softly on his nose bone, and as he lowers, you gently ask him to tip his head toward you. not twisting (that is , NOT having the mouth move toward you while the ears go farther away). no, I mean that he tucks his head so that the jowl tucks into his neck and he swivels at the poll and turns toward you. hold him for a sec with the absolute lightest touch you can, and if he takes his head back use a light but sharp tapping of your fingers on his nasal bone, on the offside, to ask him to curl back toward you. when he holds it soft, take your hands away , don't touch him but just verbally praise. and wait, and repeat.
I used to ride a 17hh giant. he did this evasion, and I never did get good at getthing to keep his head down. but, that's because I didn't take the time to do it. I just wanted to tack up and ride, not "work" on gettring things better.