The poem starts with a metaphor in which the speaker compares a woman he has just met to "a Phantom of delight." This metaphor suggests there is something deliciously unreal or otherworldly about this woman; she is some sort of enchanting spirit, not entirely solid or human.
The speaker reiterates this impression in line 3, calling her "A lovely Apparition"—or a beautiful ghost—apparently "sent / To be a moment's ornament." In other words, he thinks she's a beautiful decoration, but that's about it.
He goes on to compare her to "A dancing Shape" and "an Image gay." This suggests he's struck by her form the way a person might be captivated by a work of art: the sight of her "haunt[s]" him, surprises him, and even "way-lay[s]"—or traps—him, perhaps suggesting that he can't stop thinking about her. These metaphors all imply that the speaker's first glimpse of this woman is an intense one; he can't not notice her.
At the same time, they imply that he's only drawn to her in a shallow way. He's mesmerized by the way she appears, but he doesn't actually know the first thing about her, and he seems to think of her more as an alluring object than a person with thoughts, feelings, hopes, dreams, etc.
There's also a metaphor at the end of the second stanza, where the speaker refers to the full range of human emotions and experiences—"transient sorrows, simple wiles, / Praise, blame, love, kisses, tears, and smiles"—as "human nature's daily food." This metaphor implies that one cannot live without feeling and expressing love and its corresponding emotions.