A cover letter is an essential part of the job searching process. It is the first impression and therefore it is important to make a good impression. A well-written cover letter with supportive resume will make your application better and make a winning impression.
A cover letter tells employer that you are aware of their requirements/needs, you are interested in this job and the skills, abilities, experiences, qualification and extra efforts you have.
Cover letter should speak directly of your skills and education that make you an eligible and qualified candidate for that particular job.
There are numbers of management jobs available, where along with qualification, candidate's personality is also important. This page gives information about management cover letters. The applicants describe their qualification and why he/she is capable for this position.