Grooming certainly strengthens the bonds between you and your horse.
When I am grooming, it helps me relax and forget any problems. I concentrate on the horse and making them clean and comfortable. You can detect any changes in their coat and condition and find any nicks and boo-boos.
I also find the tickle spots that each horse likes. It might be between the front legs, on the withers, on the face, or on the behind, but they LOVE to be scratched and tickled on that spot. One or two of mine will run up and turn their butts to me because they love to be scratched there.
Sometimes I rub a clean towel over the horse and keep doing it until they are polished to perfection. Of course, with the winter hair, they don't seem to shine nearly as much.
If the weather is bad, that is a perfect time to go groom.