Source, in addition to what others have said here, I’d like you to explain why
I will make my explanation as brief as I can. If in my attempt to do so I leave some point unexplained or unclear, do say so.
The axioms of metaphysics state: existence exists, a is a, and consciousness is conscious (of something). Metaphysics thus states that existence (reality) is knowable, because - if you observe the axiom of consciousness, it states that consciousness is conscious of things that exist, and only of things that exist; and things that exist have identity, i.e. they are what they are and they cannot violate their own nature.
Epistemology, on the other hand, studies man’s means of grasping reality - reason. Reason presupposes consciousness. Consciousness perceives facts (existents) and reason integrates them into concepts. Reason is, therefore, capable of identifying objects it perceives (because they indeed have identity). You can see already the interrelation between metaphysics and epistemology - just try for example denying the validity of the axiom of identity (for the sake of the argument, regardless of the contradictions it will invoke), and see what happens to epistemology - suddenly, reason is no longer the right means to perceive reality, because existents have no identity; suddenly, by negating the axiom of identity, a ball can start bouncing all by itself for no reason whatsoever, or turn into a brick, then a needle and back into a ball (in Heraclitus’ formulation “one cannot step into the same river twice”). When identity is “reinstated” such apparent possibilities are elliminated.
Ethics recognizes that man’s standard of value is life. Therefore, he must act to sustain it. One thing required to do so is to gather food. To man, this does not come instinctively - he must use his mind, i.e. his faculty of reason; and reason, in epistemology, is man’s means of grasping that which is, and that which is - metaphysics tells us - is existence. Existents have identity. Some existents are nutritious, some aren’t and some are poisonous. Man must, by using his faculty of reason, establish which is which, i.e. he must identify existents by their nutritional value. When this is done, he must pursue these existents to fulfill his basic need for survival. (I am deliberately using here the terminology such as “existent” and “identify” to show the most direct link to metaphysics, and I use reason to point to epistemology, which again points to metaphysics. I could have easily said, for example “Man must know which is which, i.e. he must figure out what is edible and what isn’t” but then I am not showing that “knowing” requires reason, that “figuring out” requires reason, and the axiom of identity is only indirectly visible.) Every virtue of man is ultimately a virtue of survival, each one of them requires a process of reason, and such process is impossible if the mind contains no “data” to process. This data is collected by observing reality, i.e. that which exists. “Observing” something (whatever that might mean in the context of this sentence) that doesn’t exist, is fatal for a man who is trying to be virtuous. Think for example of the idea of god. God doesn’t exist, yet many men worship “him.” If you tried for even a fragment of a second to accept the idea of god, you would be accepting as true something that does not comply to any of the axioms. Does god exist? No. Does god have identity? No (even if you only judge by what others think of what god is, you will notice that they hold beliefs that are in many ways different, i.e. they do not give the idea any particular and consistent identity). Can you consciously be aware of god? No. What I just did was preform a test of the axioms on the idea of god. Obviously, such idea violates every axiom, therefore, according to metaphysics, this idea cannot be true. (By the way, the idea cannot be true even if it - on its face - violates only some of the axioms; a good example is the idea of the primacy of consciousness, although furhter analysis can show that it violates all the axioms - even consciousness - just like every other false idea.)
Moving finally on to politics, I can only say that a social structure should be based on reason and allow for every man to practice this faculty and all his virtues to the fullest extent. Things to identify here, have already been identified in ethics - virtues are the means to values which are the means to survival. What does man need to survive? That has already been answered.
As for art, I will only cite the definition quoted from Ayn Rand by Leonard Peikoff in OPAR. Everything else should become clear - if you have read carefully what I’ve written above - when you read the definition:
Art […] is a selective re-creation of reality according to an artist’s metaphysical value-judgements.
Edited to correct a spelling error.