Line ML-1 opened between Pinar de Chamartín and Las Tablas on May 24, 2007, with 5.4 kilometres (3.4 mi) and nine stations, five of which are underground. Both termini offer connections to lines of the Madrid Metro. The only above-ground stations are Antonio Saura, Álvarez de Villaamil, Palas del Rey, and Las Tablas. Line ML-1 serves the new neighbourhoods of Sanchinarro and Las Tablas, in the Fuencarral district.
Line ML-2 opened on July 27, 2007, between Colonia Jardín and Estación de Aravaca in the neighbourhood of Aravaca, in the western communities of Boadilla del Monte and Pozuelo de Alarcón. It is 8.7 kilometres (5.4 mi) long and has 13 stations, three of which are underground. They are Colonia Jardín, Somosaguas Sur, and Avenida de Europa. Line ML-2 also serves the Complutense University of Madrid. As part of the project, provision has been made for a future station at Prado de las Bodegas, which is subject to further development. The station will also provide a connection to the planned Metro Ligero Line ML-4, to Estación de Las Rozas.
Line ML-3 also opened on July 27, 2007, between Colonia Jardín and Puerta de Boadilla, with 13.7 kilometres (8.5 mi) and 15 stations, two of which are underground. The two are Colonia Jardín and Montepríncipe (which is in an open cut between two separate tunnels). Line ML-3 serves Ciudad de la Imagen, an employment centre with an audiovisual theme, and ends in Boadilla del Monte. The first 50 to 75 metres (164 to 246 ft) of track are shared with Line ML-2. As with Line ML-2, Line ML-3 serves the western suburbs of Madrid. Both lines are in a special fare zone designated as "Metro Ligero Oeste". Provision has been made for three additional stations on the line: Retamares Oeste, Ciudad Financiera Este, and Ciudad Financiera Oeste. None of the three are scheduled to open until further development takes place.
A new Metro Ligero line, Line ML-4, is proposed from the new station Prado de las Bodegas on Line ML-2 to Estación de Las Rozas, with a connection to Cercanías trains. The line would serve the Hospital Puerta de Hierro. Construction of the 14.3 km (8.9 mi), 24 station route is currently underway.
A tramway is also proposed for the southern suburb of Valdemoro, which would connect the Cercanías railway station and the Infanta Elena Hospital. Both were expected to open by 2011.
Lines ML-2 and ML-3 are expected to be extended from Colonia Jardín to Aluche by 2020.
The three Metro Ligero lines are operated by a fleet of 70 low-floor Citadis model 302 trams. Unlike the Madrid Metro, trams operate on the right. The trams have a maximum speed of 70 km/h (43 mph) and are capable of carrying 200 passengers, 54 seated. They are currently assembled into 30-metre (98 ft) train-sets, but are designed so that they can be expanded to 45 metres (148 ft) in the future.
The Citadis 302 model as used on the Metro Ligero is similar to those used by the Parla Tram in the southern suburb of Parla. However, those used on the Metro Ligero are painted red and blue, while the trams used in Parla are lime green.