You will usually need a cover letter to go with your resume. The cover letter is a marketing tool – often one of the first things that a recruiter sees about you. Its purpose is to advertise you well enough to secure an interview. It should represent you – your passion, energy, accomplishments, individuality and professionalism within the context of the job to which you are applying. A good cover letter should not, however, simply restate the content of your resume. Instead, it’s a chance for you to augment that content with some discussion of your work ethic, specific approaches you might take with the job you want, and to illustrate your writing (and thinking) skills.

Cover Letter Basics

University of Pennsylvania Anatomy of a Cover Letter

Virginia Tech Cover Letter Types and Samples