The two Canadian clubs meet in the second leg of the Eastern Conference Championship, with Montreal taking a 3-2 first-leg lead to Toronto's BMO Field on the banks of Lake Ontario.
It is the first time in MLS history that a Canadian team is guaranteed to advance to the showpiece game of the league's season.
Montreal's task was made more complicated after a Toronto fightback in the first leg which saw them score two away goals after being 3-0 down.
However the Impact have arrived in Toronto in bullish mood, confident that they can grab the result they need to advance to a December 10 MLS Cup meeting against the Seattle Sounders, winners of the Western Conference on Sunday.
"We can make history," Montreal defender Laurent Ciman said.
"Everyone has to understand that we have to be 200-percent focused as you don?t get to play this type of game every day. A golden opportunity is in front of us and we hold the keys.
"We have to be ready from the start."
Seattle would host the final next month only if Montreal advance from Wednesday's second leg, by virtue of having a superior regular-season record.
If Toronto overturn their 3-2 first-leg deficit they will host the final.
Wednesday's game could mark the final appearance of Montreal's veteran striker Didier Drogba, the former Chelsea and Ivory Coast star who has announced he will not return to the MLS in 2017.
Drogba, 38, is expected to feature at some point from the bench.
Toronto will seek to utilise the attacking talents of Italian star Sebastian Giovinco and United States international Jozy Altidore.
While Toronto were thrown a lifeline after their comeback in the first leg, defender Drew Moor maintains that Wednesday's return is too close to call.
"A lot of people say (we're) in a great spot with the two road goals,? Moor told the Toronto Globe and Mail.
"But I think history has shown it's difficult when you have the second leg at home and you need to get a result. We have our work cut out for us.
"I don't think there is a favourite either way. We don't think about that stuff. We put ourselves in a good position, but it doesn't matter if we don?t come, play our game and win the game."