The Madrid Metro is a rapid transit system serving the city of Madrid, capital of Spain. The system is the 14th longest rapid transit system in the world, with a total length of 293 km (182 mi). Its growth between 1995 and 2007 put it among the fastest-growing networks in the world at the time. However, the European debt crisis greatly slowed expansion plans, with many projects being postponed and canceled. Unlike normal Spanish road and rail traffic, which drive on the right, Madrid Metro trains use left-hand running on all lines because traffic in Madrid drove on the left until 1924, five years after the system started operating.

Storm Filomena was an extratropical cyclone in early January 2021 that was most notable for bringing unusually heavy snowfall to parts of Spain, with Madrid recording its heaviest snowfall in over a century, and with Portugal being hit less severely. The eighth named storm of the 2020–21 European windstorm season, Filomena formed over the Atlantic Ocean close to the Canary Islands on 7 January, subsequently taking a slow track north-eastwards towards the Iberian Peninsula and then eastwards across the Mediterranean Sea.