The Tokyo Metro is a rapid transit system in Tokyo, Japan. Other rapid transit operator in Tokyo is the Toei Subway. Network consists of 16 lines and 223 stations when both operators, Tokyo Monorail and Rinkai Line are combined. Tokyo Metro began operation in 1927 and Toei Subway did the same in 1960.
Transfers between two operators are not free most of the time. You may get discounts using travel cards to switch between operators.