The metro is a great way of getting around in Lisbon. There are four metro lines operating in Lisbon and these are easy to use and at the different stations it is easy to find the right directions to change lines etc.
The red line is useful as you arrive to Lisbon to the airport, because with this line you can actually travel directly from the airport into downtown Lisbon, and if necessary you can change to the other lines or just get up to the surface and walk to your Lisbon hotel or apartment or wherever you would like to go.
The most popular stop among tourists is Baixa-Chiado, which is the city center of Lisbon, and from here you can walk into the most popular shopping streets, enjoy the Elevador da Santa Justa or find tram 28 and go for a ride.
Take a look at the metro map beneath, and for a full sized version of the map just click it and a .pdf will open!
A single ticket for the metro costs 1,40 Euro, but if you do not yet have a Viva Viagem Card you will first need to buy that (the price is 0,50 Euro), and then you can buy the ticket later costing 1,40 Euro. Read more about the prices and how the public transportation and the ticket system works here.