Thanks in advance ????
Well, that really depends on what you are interested in, the places that interest me could be totally boring for you. There are some fantastic art galleries, the Prado and Reina Sofia to name a couple, lots of shopping, beautiful parks, churches, squares, historic buildings and monuments. I suggest you buy a guidebook, check online for tourist attractions, or get brochures from your hotel when you arrive.
Plaza Mayor is the coolest place of Madrid,try to spend a few hours before evening there!!
visit the Prado Museum and Retiro Park
Read a guide book