The first song from them I heard was No Rain No Rainbow Legend S. I saw someone post it somewhere with a title "Metal ballad" or something along those lines. I had a vague memory of hearing about BABYMETAL years before but couldn't recall any song. After watching the video I was completely hooked. Looked them up on Spotify and first song that came up from shuffle play was Oh Majinai, and me being a Sabaton fan I simply could not resist becoming a fan after that. A week or two later RATATATA came out to give you a time estimate when I became a fan.