They don't only help mold one's attitude, adventure and providing support for another friend.
However, I think that every single friend you have, they would eventually form a bond with you. This bond is not a normal bond as this bond shows us that one's feeling, mood, attitude would affect another by their closeness.
Humans are never meant to be creatures that live alone. We are always living together as a body. To live and unite all of us. That is why friends matter a lot. Even a person that fails very badly in exams. Trust me, with the right friends and environment provided for the person. That particular person will eventually start to improve and then he will definitely start to show the world that how dumb people can study as well. It's all influenced by friends. On the other hand, when there's a person with very good result would fail terribly if he hangs out with a group of bad people. That is just life. That is why one should always try to mix with the best group that you can find. Funny thing about friends is that they're like a chain. When you start influencing one, they will start to influence others and eventually the WORLD would be influenced.
However, there's always a catch about friends. I mean if we want to be influenced more by good type of friends, I guess it's not easy cause friends are still humans and they will eventually have some bad sides as well. Humans are fair, born to have good and bad sides as we are born on Earth, a place that is stuck between heaven and hell, which would be filled with good and bad. We must also know that a friend that used to be very good might be bad in the end as well. People change, and sometimes as we cling to them, they might need support too. If we are there only to cling onto them but not giving them support at all, they would eventually fall and might turn into a bad person as well. THAT is what it means to be a friend. To be supporting each other at each other's time of need.
BUT!!!
What if they wanted to be more than friends? I mean it's not wrong and it's really okay I guess since humans ARE suppose to find a spouse in their life. However, remember that every single action you do, it'll affect everyone around you. Your parents and your friends. Trust me, they'll be affected cause time would be filtered majority for that special person. It's a normal reaction really but I guess most people don't realise how much they affect each other. Friends that are always supporting you. The most important pillar in your life, imagine what if the pillar moved and shifted away further and further from you just because they wanted to spend more time with their spouse. The building will eventually fall and we would too. So do remember that every single thing you do affects your friends! Make sure if they're okay with it before you make any funny moves. Just like what if you suddenly dated your best friend's ENEMY! I mean it'll be terrible cause definitely it'll affect the closeness of you two as your best friend would like to always see you and talk to you but when they notice your date there, they'll definitely go away and all. Just like if you dated your best friend's CRUSH! It'll be troublesome and all alright.