A cover letter enhances your resume. While your resume establishes your qualifications, skills and ability to do the job, the cover letter communicates why you want the job and how you will approach the job. If you anticipate the most obvious interview questions, "Why do you want this job?" and "What will you do in this job?" you can gain a great advantage by proactively offering these answers in your cover letter which then serves as the perfect outline to prepare for your interview.
Cover letters should be:
Read our Cover Letter Guide for more details and a sample