The cover letter of any official letter should include the main positive points of the candidate.
Explanation:
It is best to try to put everything that will make it hard for the company to not hire you. In other words, you are selling yourself as the best candidate for the job to them and making sure that you got your best options available. So, an applicant's cover letter should give compact details about one's qualifications, what position one is applying for, why s/he should be hired and why s/he is the best candidate for the job.
The body of a cover letter tells the hiring manager what position you are applying for and why the company should select you for an interview. You are trying to sell your candidacy to the reader, so it is important to be specific about your qualifications<span> as they relate to the position that you are applying for.</span>
