What is the difference between...
- We are married for 5 years.
- We have been married for 5 years.
We are married.
This means we are married right now. It has no duration. It's now.
We have been married.
In the past we existed in the state of marriage. This state occurred for some amount of time, starting in the past, and continuing until a later point in time, which may be the present. It has a duration, but we don't know how long.
We have been married for five years.
In the past we were married. This lasted for five years. It's implied that the end of the five years is now, meaning we're still married. If it lasted for five years, but started more than five years ago, then I would expect "we were married for five years", as the state of marriage is now wholly in the past.
We are married for five years.
This is nonsense. We are married now. How can now last for five years?
That being said, this could possibly be used in an informal, nonstandard register. In comments, Edwin Ashworth gave a good example of someone telling a story:
So, we get hitched. We are married for five years. This other guy shows up....
Number 1 is a typical mistake for English learners (depending on your nationality). Number 2 is correct because the present perfect is used here to describe an action, or rather a state, which began in the past (5 years ago) and continued uninterrupted up to the present. That's exactly what this special tense is meant for, that is give you a "double perspective" on a certain situation by giving you simultaneously 2 pieces of information, one regarding the beginning of the action in the past and one concerning its persistence in the present.
The present simple alone, instead, merely states whether a certain action, state or condition exists at the moment of speaking. "We are married" is as much as you can say in this context, since the present simple cannot provide any information which goes back in time in any way.
When you talk about an action or a status that began or took effect in the past and is still going on (or valid), then any of the following tenses should be used:
Present Perfect or Present Perfect Continuous.
Thus, "We have been married for five years." is correct.
(have been is the verb to be, in present perfect tense - We got married five years ago and still remain married)
Here's another example: "We've been living in Japan for five years."
(have been living is the verb to live, in present perfect continuous tense)
On the contrary, if you say, "We are married.", it only means you're not single. You cannot use simple present tense to refer to an action or status that began in the past.