How to explain why you are applying for the position?

All companies will want to know why you applying for a particular position. This not only means explaining why you want the job but why you think your particular skills and experience would be valuable to the firm. (I am particularly interested in the position you offer as I know my previous experience and academic background would be valuable in this area of…. I am sure I would be successful in this post as I have now gained the experience and skills that are required.)