Create a wood enclosure for the metal post by wrapping a metal bracket around the post, and then secure two-by-fours in a square around the post using a drill and screws.
Paint the posts the color of the fence. Spray on a coat of spray primer; then spray the posts the desired color. If you go this route, cover the wood portions of the fence with plastic, paper or a drop cloth while you're spraying the posts, so you don't get paint on the wood.
Plant a vine or other plant that will grow in front of the fence post or climb around it. If you don't mind the rest of your fence being used as a trellis, plant a clinging-type vine such as Virginia creeper (Parthenocissus quinquefolia), hardy in U.S. Department of Agriculture plant hardiness zones 3 through 10, or Boston ivy (Parthenocissus tricuspidata), hardy in USDA zones 4 through 8. Both will cling to nearly any surface -- including your metal posts and the wood portions of your gate -- so you may have to do some training and pruning to get it to grow where you want. Another option is to place a planter or urn in front of the post with an upright, spiky plant such as Mother-in-law's tongue (Sansevieria trifasciata), hardy from USDA hardiness zones 10 to 12, or arborvitae (Platycladus orientalis), hardy from USDA zones 6 to 10.