The 19-year-old forward, who is scheduled to stay with the Ligue 1 outfit for six months, joins with the club sitting just three points clear of the drop zone and having not won for 10 matches.
But Niang is hopeful an increase in first-team appearances can help him rediscover his best form and, in turn, inspire an upturn in Montpellier's league performances.
"Above all, I've come here to get game time and also because the club has a clear objective: beating the drop, or doing even better than that," he told mlactu.fr. "So we'll try to pull together to collect points, to work closely as a team to achieve our goals.
"I spoke at length with (new Montpellier coach) Rolland Courbis. Before taking a decision, we talked it through.
"The coach clearly outlined what he is expecting of me and I told him what I wanted to bring to the side. Straight away there was a good feeling. That's why I'm in Montpellier now."
And Niang is eager to prove himself as a more than capable footballer, having been short of first-team chances at Milan, who he joined from Caen in 2012.
"I will give my all and try to offer some variety up front, while doing my best to play well with my attacking teammates," he added. "I think I can bring my power and bit of experience to bear… and hopefully some goals.
"I really want to prove to people that I haven't lost my touch.
"If I can collect some confidence, I know that I can recapture my best form. If I work hard, I'm convinced that I can do that and play a lot of good football."
