I was a little show when Corey Taylor released his biography back in 2011. He did a really small acoustic tour presenting his book. It was amazing! If this doesn't count, I'd say Motionless in White when they opened the Vans Warped Tour in 2012 in Montreal.
I also went to Rufio! Not my first concert but I used to be OBSESSED with them. I was genuinely surprised when I saw that the singer was doing all the guitar leads live while singing! So rad...My first concert was Gloria Trevi when I was a wee little kid. My first real concert I chose to go to was Sunny Day Real Estae. After that show my whole world changed.
They were my first and definitely set me up for life LOL I just love the music and the band themselves. And yes it’s amazing how our first shows shape us! @don_villa