Ibrahima Niane scored Metz's consolation goal as they bowed 3-1 to Rachid Ghezzal's AS Monaco in a French Ligue 1 encounter at Stade Louis II on Sunday.
Fredderic Hantz's men came into the match with dreams of easing their relegation worries but it was compounded despite the Senegal international's effort.
Jorge Marco de Oliveria Moraes got the hosts' opening goal just before the halftime break.
On return from recess, Metz suffered a huge blow when goalkeeper Eiji Kawashima got sent off in the 50th minute, forcing lively Jonathan Rivierez off for Quentin Beunardeau.
In the 67th minute, Monaco capitalized on their numerical advantage to increase the tally through Rachid Ghezzal after his superb curling shot breezed past Beunardeau.