We often take it for granted that a horse will wear a rug and be happy in it. My own involvement all started because Petra was so petrified of a rug. In Maverick's case he has been introduced to rugs very carefully and slowly and he is absolutely fine while it is put on and wandering around the yard.
However, once he is in the field, he is plainly worried about it and would rather stand like a statue than move around in it -he prefers not to look at either. Whilst he could live rug-less forever, it's good to have the option of putting one on but simply leaving him there to 'get used to it' wasn't doing any good.
His owner and I decided that we would have to intervene and so we tried offering him tasty things like carrots to see if we could persuade him to drop his head and neck with it on. I also used gentle body language, just as you would with loose schooling or long reining, to ask him to move. I crossed from left to right behind him to encourage him to find me with each eye in turn and therefore to see the rug in place. Occasionally I put him up into trot, taking the pressure of the body language off so that he would come back down into walk after just a few strides.
Maverick's owner tells me that he does seem more relaxed in the rug now and hopefully he will wear it like a second skin very soon. Incidentally, this rug is a little snug and he will be getting another one, but it was happening whichever rug he was asked to wear.