According to the digital sheet music published at Musicnotes.com by EMI Music Publishing, "Love on Top" is mainly written in the key of C major with a tempo of 99.2 beats per minute. Beyoncé's vocal range in the song spans from the low note of G3 to the high note of B5. "Love on Top" is set as "both a sweet love song and an expression of girl power" as stated by Georgette Cline of AOL Music. Genevieve Koski of "The A.V. Club" and David Amidon of PopMatters noted that "Love on Top" features "mature lyrics" alongside Beyoncé "sounding vocally giddy and aggressive while portraying the message." Lyrically, the song finds Beyoncé as the female protagonist expressing the happiness she feels to have her love interest in her life. "The languid, synth-soul smoocher allows for enjoyably euphoric tone" before she chimes in with "Bring the beat in!", introducing "a mid-album interlude of mid-[19]80s pop", as stated by Andy Gill of "The Independent" as well as Hamish MacBain of "NME". Rich Juzwiak noted that Beyoncé "ecstatically and hyperactively" changes keys four times during the entire song. As stated by Scott Shetler of PopCrush, she constantly sings praises of her love interest in the first verse where she also seemingly sends him subtle digs as he did not give her his full attention in the past, this being illustrated in lyrics such as, "after fighting through my fears [...] finally you've put me first." The chorus, complemented with sweet backing harmonies, then arrives, with Beyoncé chanting, "Baby it's you, you're the one I love / You're the one I need / You're the only one I see / Come on baby it's you / You're the one that gives your all / You're the one I can always call / When I need you make everything stop / Finally you put my love on top." The chorus carries the final two minutes of the song through four key changes, proceeding to D major, then to D major, E major and finally to E major. This was highlighted by Henderson who wrote that "the spirit carries both her and the song into a Stevie Wonder-reminiscent climax of continually rising key changes." In this way, the word "baby" is said about 24 times throughout the song.