There are several synonyms for the phrase "be keen on," which means to be enthusiastic about or interested in something. Some other ways to express this idea include being fond of, eager for, passionate about, enthusiastic about, interested in, devoted to, enamored with, and zealous for. Each of these phrases conveys a slightly different nuance, but they all communicate a positive feeling of excitement and enthusiasm towards something. Whether it's a hobby, a career, a friendship, or a cause, being keen on it means that it brings joy and fulfillment to your life. So go ahead and find something you're passionate about and be keen on it!