 "Army of Me" garnered mixed reviews from music critics. Andrew Hampp for Billboard and Chris Younie for 4Music both though that "Army of Me" could have been a potential single, the latter of whom writing "This track must be a future single." Younie continued to write that the song "captivates and excites right from the very start", has a "euphoric" energy and is the type of "angry" pop song that Kelly Clarkson "would give her right arm for". Sarah Rodman of The Boston Globe described it as a "Gloria Gaynor-meets-Depeche Mode dance of anger." Mike Wass for Idolator wrote that although "Army of Me" is a "quality" song, it is an album filler. Writing that it sounds as though it would have been a good song to include on her previous studio album, Bionic, Wass thought that Aguilera was "not exaggerating" when she refers to it as "Fighter 2.0". He concluded his review by saying that although her vocals are sparse, it is a "quirky" addition to Lotus. The A.V. Club's Annie Zaleski described Aguilera as a "playful" and "sassy techno diva" on "Army of Me".
