Medical school letters of intent (or what some applicants jokingly call "love letters") can be used for several types of applicants:
1) Those who have been wait listed
2) Those who have been interviewed but have not yet been accepted or rejected
3) Those who have not yet been invited to interview
When writing your letters of intent (LOIs), you should have the following principal goals:
1) Restating your interest in the institution
2) Positioning yourself as a distinctive candidate
The biggest error I see in LOIs is too much content about a specific institution's advantages. There is no reason to spend a paragraph or more telling medical school admissions members what makes their institution special. They already know! Using your precious space this way is an opportunity cost, keeping you from fully showcasing what makes you a compelling applicant.
For those of you interested in LOI assistance, please contact me. I do offer a popular LOI editing service.