What are the features of an application letter?
An application letter should be professional and to the point. The purpose of an application letter is to get the recruitment person to look at the attached resume or application, no more.
The first paragraph should tell the specifics of why you are writing, include the position you are applying and how you know about the opening. That's all for this paragraph.
The second paragraph should tell the recruiter why you are suitable for this job. Avoid terms like "I feel", "I think", or "I believe", these are qualifiers for whatever you're telling them, giving them an opportunity in their mind to disagree. Use concise wording such as, "I have performed..." or "I am ..."; use bullets if you're listing more than three or four. That's all for this paragraph.
The third paragraph (known as the call to act paragraph) should request contact to make an appointment for an interview, with your contact number (email address) at the end. Even if this info is at the top of the letter, end with it so the recipient will be subliminally directed to use it. That's all for this paragraph.
The application letter is not the place to tell all about yourself. Your resume or application should tell them your history and qualifications. The interview is the place to expand on what you want them to know about you. A busy hiring manager does not want to wade through paragraphs of text to find the pertinent information and if there a large number of applicants, will move on to the next one if your information isn't quickly accessible at a glance. If there is anything additional to add to the above, it would be what you know about the company and their goals. That should be an addition to the first or last paragraph, and no more than an additional sentence.