The purpose of a letter of intent (LOI), sometimes called a cover letter or letter of interest, is to highlight aspects of your CV relative the position you're applying for to get an interview. From the program’s perspective, the LOI is read to decide whether the candidate has the relevant skills, abilities, and experience for the position; good written communication skills; and goals and interests that match what the program offers.
Developing a LOI is often the most difficult part of the residency application process for many candidates because they must promote themselves and their achievements. This can feel uncomfortable, especially when just starting out in your career. The key is to substantiate your attributes with detailed experiences and to reference specific achievements. For example, describe what you accomplished in your duties as class president rather than simply state that you held this position.
Two notable things you can do is to show the program that you have done your research and make connections with the program. Even better is when you can show how your experiences so far have helped prepare you for particular aspects of the program or how components of the program will specifically help you in your professional development and career goals. The letter should be tailored specifically to the program, and you should avoid writing a generic letter for each program. This demonstrates to the program that you have put a lot of effort and consideration into the process. Some tips to keep in mind to help your LOI stand out include making the letter flow, transitioning well between paragraphs, and showing how the information in each section interrelates and points to you as a good fit for the program.