Whether you work in a relaxed environment or a rigorous one, your boss is your boss. They sign your paychecks, approve your hours and ultimately can make the decision to keep you around. You should always try to have a good relationship with them as that will benefit you, but pay attention to that relationship. Don’t be trying to ask them out to drinks after work every day, but maybe the occasional one. Your boss does not want to be pestered with you brown nosing. Make sure what you do say to them is appropriate for the work environment.
If you want to talk about the football match, keep it opinion free or lighthearted. When you throw your strong feelings into the mix then things may become personal. You don’ know if they like the same team as you or feel the same about the match. Do not talk to them as if they are your childhood friend unless they are then don’t do it in front of other employees. Your boss does not want to talk to you about the time you did something totally inappropriate with your other friends.
Also try to keep things positive if you can. Nobody likes a negative person. Refraining from anything political is also a good choice. It’s kind of like the football scenario where you really won’t know how they feel about a subject until it’s too late. Keeping things neutral and opinion free is always a good decision when talking to your boss. At the end of the day the you are not there to be your bosses friend. You are there to do the work they task you with in an efficient manner. You may develop a good relationship with your boss and that can help you out in the future with references, but always be aware of what you’re saying to the person in charge.