John Donne is a really punny guy. Not only that, he wrote some deeply religious poems. So, at first glance, we're tempted to immediately assume that a poem titled "The Sun Rising" is going to be about the resurrection of Jesus. But with Donne, it's pretty much God, death, or women, and we figure out pretty quickly that there isn't much of a religious overtone to this one. And death never sets foot in these verses.
Still, the title does set the scene. Quite literally, actually. We know almost immediately that this poem will be in the tradition of the aubade, a poem or song written at dawn. This isn't just a sunrise poem, though; it's actually a direct address to the rising sun, an apostrophe.
Finally, we ought to notice the verb tense. It describes the present action of the sun. We are being dropped down into a moment as it is happening. We aren't supposed to be picturing some poet composing at a desk after the fact. We are supposed to picture these two lovers in an intimate moment, just as the first light begins to creep into their bedroom.