Food is not the most important part of the day however it's important in it's own right! After all many of your guests will be with you all day and you don't want them to be hungry. There are 3 types of food to consider for the day:
Canapes: usually served after the ceremony while you celebrate your new marriage status with your guests, and a pre-order to the main meal of the day.
Wedding breakfast: can be a sit down 3 course meal or a "sit where you want to" buffet and usually the biggest meal of the day...and normally quite late so good timing to fill bellies.
Evening buffet: comes out just after the evening guests arrive and the first dance happens, or in the middle of the after party depending on the timings of the day.
The menu you select is up to you as a couple however it's worth bearing in mind that you will have guests with different tastes and dietary needs, so on your RSVPs make sure to ask people if they have any special requirements around food so your supplier or venue can cater for them too.
The best way to decide on a menu is to ask your caterer for a tasting. When I got married we went for a tasting at our reception venue which consisted of the dishes they serve for weddings but in small portions and they also gave us a sheet of paper to say what we thought of each. We had quite a few guests with dietary requirements and the kitchen were happy to cater for that. Also bear in mind that after the lunch is usually dancing so you don't want anything too heavy!
For the evening you could have a buffet of standard food for evening guests, however, you could also do something more fun like a pancake stall or a spit roast. Really it's up to you for how you want to do it on the day!