Some idioms that relate to fun and enjoyment are: in full swing, with bells on, chill out, in one's element, blow away the cobwebs, footloose and fancy free, feast your eyes on, full of the joys of spring, happy-go-lucky, guilty pleasure, have a ball, have the time of your life and let one's hair down. Additional idiom examples include: have a whale of a time, have a blast, life and soul of the party, and live the life of Riley. Idioms are phrases with meanings that aren't related to the meanings of the individual words in the phrases, and another idiom for fun would be to paint the town red.
More idioms for fun and enjoyment are: more fun than a barrel of monkeys, ring out the old year and ring in the new, social butterfly, take it easy, tickle the ivories, wet the baby's head, the world is your oyster, poke fun and for kicks. Other examples of idioms include: for the fun of it, it's all in good fun, fun and games, on cloud nine, grinning from ear to ear, grin like a Cheshire cat, happy camper, jump for joy, happy as a flea in a doghouse, life is just a bowl of cherries and on top of the world.