Two games over the space of four days will decide both clubs' fate, as Les Verts seek a return to the elite and Les Grenats try to retain their place in the top flight.
Match preview
After a late stumble saw them miss out to Angers for automatic promotion, Saint-Etienne finished third in the final Ligue 2 table, earning themselves direct entry into the second-tier playoff final.
Hosting Rodez AF last Friday, Les Verts went in front on 64 minutes, via Irvin Cardona's near-post header; after another tense half-hour, substitute striker Nathanael Mbuku wrapped matters up with a cool finish.
Currently the subject of a takeover bid, Saint-Etienne have already improved on last term's eighth-placed finish, which saw them fail to earn promotion back to Ligue 1 at the first attempt, and will now try to give their potential new owners a higher platform to build on.
Ahead of Thursday's first leg, the Loire club have only lost five times and conceded 14 goals in home fixtures this season, so head coach Olivier Dall'Oglio can be confident of earning a lead to take into Sunday's decider.
Saint-Etienne most recently met Metz in Ligue 2 last season, when Les Grenats won both matches en route to promotion, but their opponents have much more to lose on this occasion.
Metz only survived automatic demotion from Ligue 1 by the narrowest of margins, as Lorient were relegated despite winning 5-0 on the final day and Laszlo Boloni's side stayed afloat due to a slightly superior head-to-head record.
Having scraped into the playoffs by the skin of their teeth, Les Grenats will now aim to halt a four-game losing streak and make the most of their second chance.
They followed a last-gasp defeat to Strasbourg with a 2-0 loss to champions Paris Saint-Germain on the last day of the 2023-24 campaign, ultimately finishing 16th on their top-flight return.
Perhaps unsurprisingly, Les Grenats had only a 24% share of the ball against PSG - their lowest rate all year - but that matched a trend of struggling to impose themselves: ending the season with an average possession of 35%, they posted the worst rate since such statistics were first recorded in Ligue 1, some 18 years ago.
Furthermore, Metz conceded 30 first-half goals in 34 games, including no fewer than 14 during the first 15 minutes, which should bolster Saint-Etienne's hopes of getting off to a fast start.
Boloni's boys had, however, scored in 11 successive matches before being shut out by PSG, and with in-form striker Georges Mikautadze on hand, they will expect to put themselves in a position to finish the job back at Stade Saint-Symphorien on Sunday.
Saint-Etienne form (all competitions):
W
W
D
D
L
W
Metz Ligue 1 form:
W
W
L
L
L
L
Team News
Saint-Etienne should name a very similar XI to that which started their win over Rodez last week, as Olivier Dall'Oglio seeks a vital first-leg lead.
First-choice goalkeeper Gautier Larsonneur recently recovered from injury and is set to start again at Stade Geoffroy-Guichard, while midfielder Thomas Monconduit is also back in action.
Augsburg loanees Nathanael Mbuku and Irvin Cardona both scored on Friday night, but Mali striker Ibrahim Sissoko will lead the line up front, having made a significant impact in his first season at the club, with 13 goals so far.
Meanwhile, Metz can turn to last season's Ligue 2 Player of the Year for inspiration in the final third: on loan from Ajax, Georgia international Georges Mikautadze had scored in six consecutive Ligue 1 games before missing out against PSG.
Ablie Jallow, Benjamin Tetteh and Joel Asoro are the visitors significant injury absentees.
Saint-Etienne possible starting lineup:
Larsonneur; Macon, Batubinsika, Nade, Petrot; Cardona, Moueffek, Monconduit, Chambost, Cafaro; Sissoko
Metz possible starting lineup:
Oukidja; Colin, Herelle, Sane, Udol; Camara, Jacques, N'Doram; Van Den Kerkhof, Mikautadze, Diallo
We say: Saint-Etienne X-Y Metz
Defensively dubious but boasting one of French football's most potent strikers, Metz can hold out for a score draw on away soil.
Saint-Etienne have not been convincing in recent weeks, so they may be content to simply stay in the tie ahead of Sunday's return.