The app has quite a few useful features. There is a complete, up-to-date metro map so you can see its overall design as well as a route calculator to help you figure out the shortest way to get from place to place.
You can also use your device's GPS system to easily locate the closest station, and even filter stations according to the services they offer (like phones, elevators, and other things).
The app also keeps you up-to-date on the ticket types and passes you can purchase as well as how much they cost, so you won't be caught by surprise if fares go up.
Madrid Metro Official is a useful tool for anyone just getting to know Spain's capital city. Also most of its features don't require an Internet connection, which is great if you're traveling from outside the country or in one of the stations that have no connection.