Music has the power to make you happy when your sad, more energetic when you are tired and can make a bad workout a great one!
For me music creates an escape and an outlet from the stresses of my day. I go to the gym because I need that stress release, I need that time to myself and music just enhances that. There has been many times where I have been unmotivated to train and come up with every excuse in the book why not to do it, I'm tired, I'll do it tomorrow, traffic will be bad, I'm finishing work late etc.
As soon as I put my workout playlist on these excuses melt away and it puts me in the zone, ready to train, excited to workout.
I train to de stress and music just enhances that, I always feel better, more relaxed after a session and feel ten times better than I did before the workout.
Music will make you train harder, push yourself that bit further and provides motivation. I am more focussed and get my session done quicker and more effectively as there are no interruptions, just me in my own head space.
A good playlist will make the toughest workouts seem easier, more enjoyable as it will decrease how hard you think the workout is. You're not focussing on the whole workout but the music and the exercise you are currently doing. Not thinking ahead, just in the moment.
I love sticking my headphones on and cracking on with a workout, it's my time!