A leave letter for your own marriage is used to inform your employer about the time off you'll be taking for your marriage/ceremony.
If the letter is being sent as a hard copy, then it should be in the proper business format, otherwise, if the letter is being emailed, it should have an appropriate subject line and proper grammar.
I am writing to inform you that I'll be getting married on May 23 of this year. I am requesting to take May 20 to June 10 off; this will give me adequate time to prepare for my wedding ceremony beforehand and go on my honeymoon immediately following the ceremony.
In my absence, Julie has agreed to cover any emergency situation that comes up related to my accounts.
Your formal invitation should be going out within the next couple of weeks. Thanks in advanced for your consideration.