Tavenot will be desperate to shore up a Metz defence that had conceded more goals per game pre-round than any team in Europe’s top five leagues this season (2.2), but the first half illustrated the size of his task.
Lyon took the lead after 11 minutes when captain Corentin Tolisso plucked a long ball out of the sky and pulled it back for Endrick, who tucked home to open his account in the league after arriving last month.
Les Gones doubled the advantage five minutes later, as centre-back Ruben Kluivert prodded Khalis Merah’s teasing cross past Metz goalkeeper Jonathan Fischer to score his maiden Ligue 1 goal.
Endrick had the ball in the net again after 22 minutes only to be flagged offside, but the visitors’ third goal arrived 10 minutes later as Tyler Morton bagged his second of the season with a ferocious low drive from the edge of the penalty area.
The hosts quickly hit back, as Koffi Kouao latched onto a loose pass to race clear and roll the ball home for his first Metz goal.
Lyon soon restored the three-goal lead, though, as Endrick outpaced the home defence in first-half stoppage time and side-footed through Fischer’s legs.
It was the second successive home game in which Metz had conceded four goals, following a 4-0 Coupe de France thrashing by Montpellier a fortnight earlier.
Endrick had two chances to complete his hat-trick early in the second half, but Fischer first pushed his header around the post and then got down well to save his low effort.
Metz kept going, though, and Habib Diallo gave them hope in the 64th minute with his fourth goal of the season, the forward converting Kouao’s wicked cross with a fine first-time finish.
Endrick may have thought his chance of a hat-trick had gone, but the 19-year-old gave himself the perfect opportunity when he was tripped in the penalty area late on.
The Brazilian striker picked himself up and converted the spot-kick low to Fischer’s right, sealing his treble and condemning Metz to their fourth successive home defeat across all competitions. Meanwhile, Lyon march on with a victory that narrows the gap to third-place Marseille to two points.