Epistemology is a facet of philosophy interested in knowledge. And an epistemological question is a question concerned with something relating to knowledge, apprehension of knowledge, knowledge-world correspondence, or the origins of knowledge. What is knowledge? Is knowledge even possible? If so, how do we get it? Does knowledge correspond to reality? How do people acquire knowledge?--Is it from the world or from our experiences in the world or do we have it before we experience the world?
Metaphysics is a division of philosophy interested in figuring out exactly what being is. Basically any kind of question about what is, natural or supernatural, including science and religion, is a metaphysical question. Some of their perennial questions are what is the difference between particulars and individuals? Is there a reality out there? What is reality? Is there a god? What is god? Is free will a possibility? Is change possible? What is identity? How much control do agents have control over their actions?
And though these two philosophies overlap in some places, they have three major differences. First, epistemology is almost always focused on being a living thing, because even if one investigates whether or not knowledge corresponds to the world, an agent is still necessary to see uncover the knowledge there. Second, metaphysics is very often focused on the differences between things, and while you could ask the question "Is there such a thing as knowledge?" in both an epistemological and a metaphysical context, your answers could be very similar, but will likely be different. They'd differ because epistemologically, asking the question will usually break down into questions about the justification for beliefs and knowledge; whereas a