Victory moved Marseille onto 15 points, ahead of champions Paris Saint-Germain and surprise packages Lyon on goal difference with the latter two still to play this weekend.
Abdallah Sima scored with virtually the last kick of the match to hand 10-man Lens a 2-1 victory at Auxerre and move the northerners up to fourth.
Rock bottom Metz parked the bus in the first half but Marseille poured forwards after the break with Brazilian dynamo Igor Paixao breaking the deadlock on 51 minutes, while Matt O’Riley on 69 minutes and Amine Gouiri two minutes after that secured the three points.
“These are the kind of matches we were losing last year, we’ve matured and the team is much stronger now,” said De Zerbi.
“I’m very happy.
“This is my best period since I took over Marseille,” the Italian coach, who joined from Brighton in June 2024 and led OM to the runners-up spot last season, added.
Marseille had a rocky start to the season with a dressing room fight after an opening day slump paving the way for star midfielder Adrien Rabiot to be transfer listed, before joining AC Milan.
De Zerbi described the altercation between Rabiot and English winger Jonathan Rowe — who moved to Bologna — as being like a bar room brawl.
Before Saturday’s romp over bottom side Metz, Marseille beat Ajax 4-0 in the Champions League after wins over PSG and Strasbourg in Ligue 1.
Marseille, who last won the title in 2010, also climbed top briefly last Friday after their 2-1 come-from-behind win at Strasbourg.
Lens took an early lead at the Stade de l’Abbe-Deschamps through former Crystal Palace forward Odsonne Edouard.
Francisco Sierralta equalised for the lowly hosts just after the hour mark and when centre-back Piere-Ismaelo Ganiou was sent off with 17 minutes to play, Lens’s hopes of victory seemed slim.
But Sima had the last word.
In the day’s other match Brest and Nantes played out a goalless draw.
PSG, who have won Ligue 1 in the last four years, travel to Lille on Sunday while Lyon host Toulouse, with either able to take over top spot if they avoid defeat.