Objectively speaking, in that arrangement, the letters used to serve as a 'cover' _ that is, or the front page, to the whole job_hunting document, which apart from incorporating the curriculum vitae or resume, typically also tended to enclose certified copies of ones academic and professional credentials. The days when the letter used to literally cover the job_hunting documents might be long gone (as we mostly send applications, Curriculum vita or resumes and copies of certificates online as email attachments), but the cover letter has still not outlived its usefulness. The letter is the document that nowadays provides introduction to the whole job application attachment, 'and where it is all coming from. 'There are a number of formats that can be employed in drafting a cover letter whenever job hunting, depending on factors like the job that is being sought and the jobseeker's preferences.
Make sure you choose a cover letter format that you feel most comfortable with. It should be something that could best express your personality but keeping it as formal as possible. Be wary of the details of the cover letter format. It must be clean and neat. It should provide the data directly. There is no need to be colorful or playful with the fonts.