From 1861 to 1886, the Montreal City Passenger Railway Company operated a small network of horse-drawn trams (also called streetcars in North America).

The company underwent another name change in 1893: MSTR became the MTR for Montreal Island Beltline Railway.

Commuter trains ceased to be the managed by the STCUM in 1996 and responsibility for this service was transferred to the newly created Agence métropolitaine de transport.

The streetcar network had its beginnings with the horsecar era of the Montreal City Passenger Railway in 1861.

By the end of 1985, the STM (then known by the initials CTCUM) had exited the regional bus business to focus on its core territory (the Island of Montreal).

Most of the regional bus routes were passed to private operators who provided services under contract to newly formed intermunicipal transit councils.

The CTCUM paid CN to staff, run, and maintain the trains, while it set the fares and schedules.

[8] On January 1, 1996, responsibility for the commuter trains was transferred to the Agence métropolitaine de transport (AMT) (now Exo), a Quebec provincial government agency formed to coordinate all public transportation in the metropolitan Montreal region.

Passengers leaving the island of Montreal are expected to keep proof of payment of a paid fare that covers zones A and B.

[9] Beyond standard ARTM fares, the STM area has the following particularities: As of February 2022, the STM no longer accepts cash at Metro stations (cash is only accepted for bus fares); only debit and credit cards can be used to purchase tickets.

In preparation for this new step in Montreal's public transportation network, turnstiles which incorporate the reader and automated vending machines had already been installed in Metro stations; buses had previously been fitted with new fare boxes that incorporated the card reader in order to ensure the uniformity of methods of payment across Montreal's transit network and that of its suburbs.

It includes electronic signs inside buses showing the estimated time of arrival at upcoming stops and the busiest bus stops have electronic signs showing the estimated time of arrival of the next bus.

As of December 2024, there are 29 stations with elevators installed: Angrignon, Côte-Vertu, Du Collège, Snowdon, Lionel-Groulx, Bonaventure, Place-d'Armes, Champ-de-Mars, Berri-UQAM (orange and green lines only), Rosemont, Jean-Talon, Henri-Bourassa, Cartier, De La Concorde, Montmorency, McGill, Place-Des-Arts, Prefontaine, Honoré-Beaugrand, Jean-Drapeau, Vendôme, Viau, Pie-IX, Mont-Royal, Villa-Maria, Jolicoeur, D'Iberville, Outremont, Place-Saint-Henri.

Their mission is to maintain peace, order and public security, to prevent and repress crime and, according to the jurisdiction specified in their deeds of appointment, to enforce the law and municipal by-laws, and to apprehend offenders.

The Metro system is Canada's busiest subway system in total daily passenger usage; in 2017, serving an average of 1,235,200 daily passengers on an average weekday; a figure which surpassed that of the Toronto subway and Vancouver SkyTrain.

However, on January 6, 2023, the STM announced it planned to permanently end all "10 Minutes Max" routes due to budget cuts and constraints caused by the COVID-19 pandemic and a decline in ridership.

[32] In the early 2010s, the STM announced a plan to convert its entire fleet of buses over to electric power by 2025.

[36] After an initial attempt in the 1990s, a bus rapid transit (BRT) line opened on Pie-IX Boulevard in November 2022.

It uses dedicated lanes, has priority at intersections and has all-door boarding to increase capacity and improve reliability on the corridor.

[37] The STM also operates ten taxibus lines where the creation of regular bus service is not feasible.

They are Anjou, Frontenac, LaSalle, Legendre, Mont-Royal, Stinson, St-Denis, St-Laurent and St-Michel for Paratransit.

Metro trains are stored in the four garages at Angrignon, Beaugrand, Montmorency and Saint-Charles and there are three maintenance facilities at Duvernay, Plateau d'Youville and Viau.

The STM is in the process of changing all its bus stop panels to a new modern pole that displays the route numbers.