The Paris Metro is one of the world’s best, and is really the only way to get around Paris that is efficient and affordable. The Metro opens at 5:30 in the morning and ends around 12:15 am.
The metro itself is worth exploring in Paris, as most of the major stations are intrinsic parts of the Parisian cityscape. The metro stations are easily recognizable as they are marked by a huge “M” or the word “Metropolitain”.
If you are going to be in Paris for more than a day or so, it is best to purchase a carte orange, which you can purchase by week or month. An unlimited weekly pass costs just €14.50 and the monthly is €48.60. Just make sure you have a photo ID with you as one is required in order to purchase your pass.