Most major job sites that assist you in job research will tell you to attach a cover letter when submitting a resume for a job that interests you. The purpose of a cover letter, or a motivation letter, is to draw attention to your resume and to help you get an invitation for an interview. In most cases, though, a cover letter is not a prerequisite for a response. But this is precisely why it is so valuable. If a company has a specific picture in mind of the candidate they are seeking, a motivational letter can help its recruiting staff determine which candidate is the most qualified for this position.