My toddler wont go to sleep?

My toddler is 2 1/2 years old. When bedtime comes around we give him his drink and kisses. Then he is taken upstairs and read a book. When I lay him down and walk out within 3 mins he runs out crying hysterically about being sacred of the "scary monster" . Everynight i turn his lights on and we check for the scary monster. He has been sleeping with me and my husband for the last month and its time for him to sleep in his room. Does anyone have any advice on how to get him to go to sleep??