Check out these pictures for inspiration that work well for the groom.
My advice is to keep the hair with a little bit of length.
The reason for this is that it will photograph better than short hair. Be comfortable and look like yourself. Either way just make sure everything is clean and groomed.
Plenty of male celebrity choose the messy look for the red carpet so it’s a proven formal hairstyle.
Slick hair is one of the most common formal hairstyles. It is preferable to use a matte product that won’t show up shiny in wedding photos. If this look is new to you get the right haircut and product to practice with a few week before the wedding or have a barber or stylist do it for you on the big day.