The Western Sydney Airport project will construct a line approximately 23 km (14 mi) from St Marys to the new Bradfield Station in Badgerys Creek.

It will comprise six stations and service the Western Sydney International (Nancy-Bird Walton) Airport, which is also currently under construction, upon its opening in 2026.

[19] Expected to cost $12 billion, it would have linked Rouse Hill in Sydney's northwest with the CBD, with construction starting in 2010 and finishing in 2017.

[20] The construction of the North West Metro was dependent upon the privatisation of the electricity network,[21] but, after a change of the state's Premier in late 2008, it was cancelled due to budgetary concerns.

[23] Reception to the plans was mixed, with Opposition leader Barry O'Farrell accusing the Premier of "making it up as he goes along" after costings were not released until after the press conference;[24] criticism came from the Greens because the route seemed designed to pass through marginal electoral seats.

[25] The Government's initial submission to Infrastructure Australia for funding was rejected due to "a lack of integrated planning".

[32] In mid-2012, the newly elected Coalition government announced Sydney's Rail Future and the NSW Transport Masterplan.

[33] Under this proposal, the North West Rail Link would be built as a single-deck, privately operated metro connecting to a future second harbour crossing.

[41] Opposing parties warned the government that the sale of the power infrastructure may not provide the capital needed.

[44] In February 2023, as part of the 2023 state election campaign, the government of Dominic Perrottet announced business cases would be produced for further extensions for the Sydney Metro network.

For the first 6 months of operation, they were supplemented with trackwork-style rail replacement buses for late-night services from Sundays to Wednesdays.

After the addition of the Stage 2 extension to Bankstown, the stations’ platforms will be configured to allow for future use of 8-car trains and the signalling system designed to allow for 2-minute headways, both of which are planned to be introduced once increased patronage demands it.

[57] The network currently operates using 45 6-car Metropolis Stock trains, which are fully automated electric multiple units.

Before the introduction of services, a full-scale model of the new train was built for use on public display, including at the annual Sydney Royal Easter Show.

Opal is also valid on bus, ferry, and light rail services but separate fares apply for these modes.

Construction of the first section of the Metro North West & Bankstown Line began in late 2013,[74] linking Tallawong, in Sydney's north-western suburbs to Chatswood.

In November 2016, Sydney Metro, in particular, the John Holland Group, Dragados and Transport for NSW, were awarded the 2016 NSW Premier's Award for Building Infrastructure for the 15 km (9.3 mi) twintunnels in Bella Vista and Epping, which are currently the longest tunnels constructed in Australia.

The NSW Premier's award recognises "infrastructure projects in the state that make a difference to the local community".

[78] The City & Southwest extension represents the first phase of the "southern sector conversion" envisaged in Sydney's Rail Future.

[80][81] The 2019–2020 New South Wales state budget in June 2019 allocated funding of $6.4 billion over four years to the project, with construction to be fast-tracked to start in 2020.

[96] The City & Southwest line is being planned to be extended from Bankstown to Glenfield[45] via Liverpool,[96] with a further potential extension to Bradfield Station via the existing South West Rail link that serves Leppington.

[33] Developing plans for this extension has proven difficult, and the Sydney Morning Herald reported in February 2016 that the project may have been dropped.

[97] The South East Sydney Transport Strategy of the New South Wales government envisions a metro line starting from the CBD with stations at Green Square, Randwick, two at Maroubra, Malabar and La Perouse built by 2041, as well as another one from Randwick to Eastlakes and, via the Domestic and International terminals of Sydney Airport, further on to Brighton-Le-Sands and then Kogarah by 2056.