I think something has happened with the formatting of enotes - when I edited your question the poem converted into paragraph form. Sorry about that! In this excellent poem by Amy Lowell, she uses an extended metaphor (one comparison that runs throughout the poem) to describe the love-hate relationship that she has with her lover. Note how as they meet, they react in a way that compares them to fireworks:
But whenever I see you, I burst apart
And scatter the sky with my blazing heart.
Note how the metaphor that compares them to fireworks allows Lowell to express their emotions and the way that their passion for one another flashes out, much as fireworks do into the dark night sky. This is the same for her lover, who when he meets her, goes up in a "flaming wonder":
Golden lozenges and spades
Arrows of malachites and jades,
Patterns of copper, azure sheaves.
Such beautiful descriptions serve to reinforce the emotions that the two characters express, which is beautifully described through the use of the extended metaphor that compare the two central characters to fireworks.
This extended metaphor of the speaker's feelings being compared to fireworks is beautifully replete with colorful and explosive imagery. Lowell, of course, incorporates other metaphors within this frame metaphor.
The speaker of the poem compares her heart to the type of fireworks that shoots into the sky, bursting with thunder, and then showers down streams of colored light against the dark sky.
my blazing heart.
It spits and sparkles in the stars and balls
The imagery of fireworks as "buds" and "disks" of myriad colors continues until the speaker encounters the person for whom she feels such antipathy. Then this other person becomes part of the fireworks:
And when you meet me, you rend asunder
And go up in a flaming wonder
Of saffron cubes and crimson moons
Lowell concludes the poem with with the speaker and her enemy meeting
As you mount, you flash in the glossy leaves.
Such fireworks as we make, we two!