Being comfortable shooting entirely manual is extremely important in all types of photography but particularly concert photography.
Rapid changes in stage lighting can easily fool the camera in any of the automatic shooting modes. The problem is that the cameras light meter will never be as smart as the human eye. I think it’s preferable to manage the exposure manually using the LCD screen and the histogram instead of trying to push and pull one of the cameras automatic modes to match what your eye sees.
Practice shooting manually in zero pressure situations. Photos of babies, cats and dogs are awesome places to start. Uh, yeah.