To be considered for almost any position, you will need to write a letter of application. Such a letter introduces you, explains your purpose for writing, highlights a few of your experiences or skills, and requests an opportunity to meet personally with the potential employer.
Precisely because this letter is your introduction to an employer and because first impressions count, you should take great care to write an impressive and effective letter. Remember that the letter not only tells of your accomplishments but also reveals how effectively you can communicate.