I want to book metro tickets for my transfer

If you have to transfer trains in Paris,there's a good chance you'll need to travel to a different station within the city. The most efficient way to get there is by taking the Paris Metro or Paris RER (fast metro). Metro fares are not included in your train ticket.

Paris metro tickets can either be bought at the train station, or online via the RATP app. These tickets are loaded on your phone after purchase (most international cards are accepted in the app) and can then be used at the station.