I am naturally a small person and I was wondering if there was anything I could do to slow my metabolism to gain weight?

Slow down. You do not need to slow your metabolism just your meals. Take your time and enjoy your meals and your friends. Put away your cell and taste your food. Thank God for every bite. Look at the person you are sharing the meal with and listen wile you chew. Then you will develop as you should. There are many that are praying they had your problem. Good health.