People get married for a wide array of reasons, and have all sorts of expectations of how marriage will change the relationship. And while it's true that turning the person you're dating into a legal partner does affect certain things, those who expect marriage to be a cure-all for all your relationship woes are sorely mistaken. So without further adieu, I present to you five things that will change and five things that won't change once you walk down the aisle.
What marriage will change about your relationship
You will feel, over time, a sense of ownership for this thing that you've just made legal. Eventually you develop a pride and respect for it that is somewhat separate from your love for your spouse. Think of it as a much smaller version of the first time you built a piece of IKEA furniture with your spouse -- somehow, you've created something that's more than the sum of its parts. This is helpful, because even when you are upset with your spouse, you can still fall back on wanting to be respectful to your "marriage".
Other people's perceptions of you will be different. Strangers might assume that you're trying to have a baby, coworkers will think of you as more grownup than single people your age, and friends you've had for years may suddenly think they can't invite you to go barhopping. This can be helpful when you're trying to do something like rent an apartment, but it can also overwhelm you if you're already feeling a bit nervous about the changes that marriage brings. Make sure that you and your spouse are creating what you'll be like as a married couple on your own, without all these perceptions clouding things.
You will probably have more "home stuff", depending on the kind of wedding you had. Bakeware, matching cutlery, nicer bedding, perhaps even some china- and this will make you feel a bit more domesticated and settled in to your new arrangement. Don't let this lull you into thinking that everything will always be fine and dandy. Things can be tough even when surrounded by nice Pottery Barn stuff.
Your financial status is now tied, legally, to another human being. Your debts are now your spouse's debts, and vice versa. How you spend your money is no longer just your business. This takes a lot of newlyweds a while to get used to, but it's what most married couples fight about, so don't go into marriage pretending like your beloved's credit history won't be an issue.
Ending your relationship is no longer just as simple as having "the talk", gathering your things, and moving out. Entering this legally binding relationship required work, and leaving it will require a lot of work as well. Please make sure you are considering this before you jump into marrying someone just because a) it's time, or b) he/she asked.
What marriage will not change about your relationship
Your feelings for your partner will not change. Marriage is not a magical potion that serves to amplify adoration, reduce deep-seated feelings of resentment, erase fears of commitment, or answer questions about whether or not this is the right move. Marriage is a ceremony that cements your current bond to another human being, and while that's a huge thing, that's all it does.
Marriage will not change your spouse. It will not make him or her more mature, more loyal to you, or better at housework. However your partner treats you now is how they will treat you once you are married, and to assume otherwise is setting you up for failure. Gut check yourself before the big day to make sure that you are not secretly hoping that this ceremony to be a "wake up call" for your relationship.
Likewise, marriage will not change you. It will not make you more mature, more loyal to your partner, or better at housework. Marriage will not make you grow up -- you have to do that yourself. Emotional development requires thought, hard work, and self-exploration, and all of that can be done with a partner, but don't assume that it will automatically happen.
Attitudes about "grown-up" things like children, religion, how to spend money, and work ethic will not be affected by marriage. People don't say vows and then immediately get on the same page about these issues- it requires tough conversations and work, work that is best done before you walk down the aisle.
The permanence of your relationship will not change. (I know this seems contradictory to what I said above, but stick with me). People often feel completely trapped once they're married, and though it is much more complicated to get out of a marriage versus a cohabitation, you are never trapped. I am not an advocate for divorce, but rather an advocate for people making the choice, every day, to be in their marriage, rather than put up with their marriage.