There is a format for writing a cover letter. Below is a guideline for writing a good looking and a well organized cover letter.
In the first paragraph mention the following things:
This paragraph is important from the point of view of detailing
Here you can indicate:
Structure and Details
Appropriately address the salutation to a specific person, not job title (spell their name correctly). Organize your letter well. Before giving your cover letter check for any spelling or grammar errors. Use an appropriate font type and size - Not to big or not to small. Don't forget to leave contact information in the letter. Write in the tone of a confident (but not arrogant) professional. Be direct.
A cover letter is your opportunity to tell the employer what you are applying for and why you are a good match for the position and the organization. You should submit a cover letter with every resume, whether for an internship or job. While a resume provides a summary of your skills and experience, a cover letter takes it a step further by allowing you to highlight your specific qualifications.