The Chennai Metro was inaugurated in June 2015; in the first few months, it was treated more as a fun ride rather than a regular mode of commute. Just when things were settling down came the heavy rains of December; the Chennai Metro came into its own, as the quickest way for people to get to the inter-city bus terminus at Koyambedu. Running high above the flood waters, the Metro's trains were indeed a lifeline for the many who went back to their hometowns, and other cities, to get away from the rain waters.
There were problems - the trains are meant to carry a little over 1200 passengers at one go - and there were about four times that many at the stations during the peak rains. The Chennai Metro did its best to dynamically alter the schedules to accommodate as many as they could. Apart from that, the spike in traffic helped the Chennai Metro figure out how their systems could take the stress.
This picture is from way before the waters, at a time when the Metro was new enough for everyone to be posing in front of its train-sets. At least the selfie-taking couple is wise enough to stay on the right side of the yellow line, unlike the hero who is trying to channel some kind of superhero!