Having taken a 13th-minute lead, Metz looked capable of extending their advantage every time they turned defence into rapid attack. West Ham had their chances and Frank Lampard missed a second-half penalty, but Harry Redknapp's team can have few complaints.
A string of absentees gave Hammers' defence an unfamiliar look, with Steve Lomas filling in at right-back and the ever-reliable Steve Potts taking a central berth alongside Rio Ferdinand. If they took encouragement from the numbers filing immediately into deep positions for the visitors, then the control at high speed with which Metz assembled their counter- attacks would soon prove to make their night an awkward one.
Crucial to the French club's hopes of scoring the vital away goal was the midfielder Frederic Meyrieu, who demonstrated the value of his invention when he fashioned a move that put Metz ahead, Danny Boffin providing the cross that enabled Louis Saha, who had three months on loan at Newcastle last season, to head in convincingly.
West Ham were unable to create anything so clear-cut and it scarcely helped that Paulo Wanchope and Trevor Sinclair were proving surprisingly easy to stifle for a French back line in which Sylvain Kastendeuch was commanding. Paolo Di Canio, operating just behind a rather blunt spearhead and showing much purpose and energy, increasingly became a figure of frustration.
There were chances for John Moncur and Lampard early on, but generally the French resistance proved well organised. Wanchope at last discovered space as Sinclair played him in, but goalkeeper Lionel Letizi pulled off the save with his legs.
There were signs at the start of the second half that West Ham could reap some reward. Scott Minto volleyed just wide, and when Lomas found Letizi half smothering his low shot a defender was on hand to clear.
On the hour Di Canio earned a penalty when his forceful run into the penalty area enticed a tug from Gregory Proment. However, Lampard's shot was saved by Letizi to his right.
West Ham United (4-4-2): Hislop; Lomas, Ferdinand, Potts, Minto; Foe, Lampard, Di Canio, Moncur; Sinclair, Wanchope. Substitutes: Forrest, Cole, Carrick, Kitson, Angus, Keller, Wright.
Metz (1-4-3-2) Letizi; Kastendeuch; Schemmel, Proment, Pierre, Gaillot; Bastien, Baffin, Meyrieu; Saha, Gousse. Substitutes: Biancarelli, Asuar, Rizzetto, Van Handenhoven, Toyes, Jestrovic, Marchal.
Referee: M Diaz Vega (Spain).