Lille, for whom Metsu played from 1979-81 and coached in 1992-93, did not give a cause of death, but media reports said he died early Tuesday following a battle with cancer.
"It is with great sadness that we have learnt of the death of Bruno Metsu," Lille said. "Lille, its president Michel Seydoux, and all the players and staff at the club, as well as the fans, offer their sincere condolences to his loved ones."
Metsu's most memorable achievement as a coach came at the 2002 World Cup, where his Senegal team beat defending champion France 1-0 on its tournament debut, one of the biggest upsets in World Cup history.
The West African team, in what remains its only appearance at the tournament, went on to beat Sweden to reach the quarterfinals before losing to Turkey, becoming only the second African team to reach the last eight at the World Cup.
Reflecting the great affection Senegalese people had for Metsu, the country's president, Macky Sall, offered condolences to his family and said the Frenchman with his unmistakable long, wavy hair helped to write "the most beautiful pages" so far in Senegal football history.
His former players also praised his popular management style.
"More than a coach, he was a big brother for us. What I liked about him was that when we had to work, we worked, when it was time to have a laugh, we laughed," Senegal striker Souleymane Camara told L'Equipe.
"His team speech before the France game ... I still talk about it to my friends. He managed to motivate us so much that we couldn't lose. He knew how to find the right words. He also showed us some footage of the atmosphere surrounding the national team, so that we would surpass ourselves."
Former Senegal midfielder Khalilou Fadiga, a key player in the 2002 World Cup team, wrote "I have lost a brother" on Twitter.
Earlier that year, Senegal also reached the African Cup of Nations final, where it lost on penalty kicks to Cameroon.
"A thought for those close to Bruno Metsu, a man and a coach who successfully exported the values of French football," the French Football Federation said.
Metsu spent his last years as a coach in the Middle East with spells in charge of the United Arab Emirates and Qatar national teams, as well as club sides Al-Gharafa in Qatar and Al Wasl in the UAE, where he replaced Diego Maradona.
Earlier in his career, he also coached Valenciennes, Sedan and Valence before taking charge of Guinea, and then Senegal from 2000-02.
Claude Le Roy, a close friend of Metsu's who also coached Senegal, Cameroon and Ghana, said Metsu "fought like a lion."
"It's terrible for him, for Viviane (his wife) and the kids. I'm thinking about them in particular," Le Roy told L'Equipe. "We had a lot of adventures together. I will remember his magnificent smile and his love of life."
Former Lille teammate Stephane Plancque remembered the fun-loving Metsu with fondness.
"We played together for two seasons. I was younger than him, I knew about him already from his reputation," Plancque said. "We quickly became close, and were roommates for away games. He was a great guy."
David Friio, a former midfielder who played for Valence and now works as a scout in France for Manchester United, also paid his respects.
"He helped me at a time nobody cared and I will never forget that," Friio tweeted.