social butterfly

this phrase generally refers to a woman, but there are no good inclusive alternatives for it. "Social butterfly" conveys a sense of light-mindedness along with the sociable, gregarious character of the person. Either use "social butterfly" for men too or consider sex-neutral adjectives and nouns: gregarious, outgoing, social, sociable, socially active, convivial, extroverted; a joiner. See also socialite.