This list of metro systems includes electrified rapid transit train systems worldwide. In some cases, metro systems are referred to as subways, U-Bahns or undergrounds. As of October 2014, 157 cities in 55 countries around the world host the approximately 160 metro systems that are listed here. The London Underground first opened as an "underground railway" in 1863 and its first electrified underground line opened in 1890, making it the world's first metro system. The metro system with the longest route length is the Shanghai Metro; the busiest one is the Beijing Subway; and the one with the most stations is the New York City Subway.

Answer this question: when was first metro train started in world? Let's give stream of consciousness first:
This is the relevant information: The London Underground first opened as an "underground railway" in 1863 and its first electrified underground line opened in 1890, making it the world's first metro system.
So, the final answer is 1890.