I agree with Barry's comment about the horse being young, yet, and you're describing a goal that comes with maturity. Also agree with Iridehorses, exactly. I have a 6 year old that I'm working on for a trail horse. He and I spent 3 years on the ground work while I was waiting to get him to the trainer for under-saddle work. Some of the things that we did were putting feet inside muck buckets and standing, walking over and under tarps, tying things to the saddle that bounced or rattled, walking through puddles, and learning how to play horse soccer with a horse ball on the ground. He was taught in the round pen that if he stops moving, the scary thing will stop (hoses, bouncing stuff, whatever - I would stop spraying or take off the bouncy thing). So, once I even tied a Superman cape out of a 8x10 tarp around his neck and sent him off in the round pen. It was hilarious - he wasn't bothered by it, took off running, did maybe a couple of laps, and stopped in the middle looking at me as if to say, "Okay, what now?" That showed me that he trusted me enough to put up with whatever I might ask. Now that we're under saddle, we ride out alone so that trust is critical. When we approach scary/new objects he might slow down and snort, but he rarely stops and has never balked. We learned the "one more step" command at 1 year old and he will take one step at a time, which earns praise and a brief rest/release of pressure. Usually that's all it takes for him to decide that the scary thing is okay.
A funny moment to share - Once we encountered the neighbor's huge tractor loaded front and back with hay bales on spikes, with a 11-bale round bale carrier - a huge rig tthat looked nothing like a tractor from our angle of approach. I asked him to walk on, and he turned his head back to look at me eye to eye as if to check to make sure that I really, really knew what I was asking. I cracked up, patted him on his face, said "one more step" and off we went. I love that fella!