Despite losing at Lens, Metz saw promoted from Ligue 2 on goals socred after Le Havre drew level on goal difference with a big win.
Metz have made an immediate return to Ligue 1, with former United States manager Bob Bradley's Le Havre falling one goal short of moving into the promotion places on the final day of the season.
Metz held a three-point lead and a superior goal difference by six over Le Havre in the Ligue 2 table heading into the final round of fixtures on Friday.
However, it suffered a 1-0 defeat to Lens at the Stade Felix Bolaert, opening the door for Bradley's team to snatch the final promotion place.