 "Beautiful" is a gentle pop ballad that discusses issues of self-esteem and insecurity, promoting a message of self-empowerment and embracing inner beauty. Larry Flick of Billboard added that the song talks about "overcoming life's trials", Chuck Taylor also of Billboard observed that it has a message of "holding oneself up against criticism from the outside," and Todd Burns of Stylus noted that the song "also explores the main theme of the record, being stripped bare in front of the public." Its instrumentation incorporates bass guitar, cello, drum kits, keyboards, piano, and violin. "Beautiful" was composed in the key of E ♭ major and moving at a slow 76 beats per minute. Aguilera's vocal range spans over two octaves from E ♭ 3 to G5; she uses several melismas in the song, fitting as many as seven notes in one syllable.
