1. An update of my med school apps (ie still no interviews). 2. What have I been doing since I sent in my apps for the master's program. 3. How their program would specifically help me (I have low GPA and high MCATs). 4. My research into the program (extensively researched the program, spoke to people who have completed the program). 5. My intent to attend the program if I am accepted.
Just put anything that would give them a reason to accept you (that is true of course).