Hi Amankaur! There's no strict format in writing to a university professor about possible research supervision. But let me share to you what I did. First, it should be in a business letter format so that it will appear formal and professional. Next, introduce yourself; specify your earned degree and from what university/country. Third is your intention to join his/her laboratory. If the professor is on multiple research topic, pinpoint which one you wanted to be involved with. Also write here why you wanted to join his group; include your job experiences, your research interests, personal strengths which may include your academic performance. Fifth, you may include your plans after graduation. Lastly, give a little appreciation regarding the they spent in assessing your credentials.
Don't forget to attach a curriculum vitae, transcript of records, IELTS scores and any document that you think will help the professor do an evaluation.
I got admission from the UofCalgary so I think I pretty did a good job about the letter I sent to my supervisor. Good luck! Hope you land in Canda soon.
