John Donne's poem “The Canonization” is filled with interesting imagery and with a special kind of metaphor called a conceit. A literary conceit compares two extremely different things in surprising yet creative ways that are both stunning and intellectually satisfying. Let's look at both the imagery and the conceits in this poem.
As far as imagery goes, the speaker applies it first to himself when he invites his implied partner in conversation to criticize “my palsy, or my gout, / My five gray hairs” rather than criticize his love. We cannot help but form a mental image with these words. He goes on to argue that his love has injured no one, and he does so again through creative imagery. No merchant's ship has drowned because of his sighs or the overflowing of his tears. Just picture that! His cold shivers of love have not prevented spring from coming. His fevers of love have not caused disease. Everyone goes on about his or her business perfectly well even though the speaker loves.
In the poem's third stanza, Donne introduces several conceits. The two lovers are both flies, insignificant and even bothersome in the eyes of the world, yet still in love. They are tapers (candles) on fire with love. They are the eagle and the dove, which supposedly fly in different circles of the air but have come together in love. They are the phoenix, burned to ashes by the fire of their love yet also able to rise again through their love. These conceits are all brief, but they are vivid and unexpected, and they force readers to think deeply about the situation of the lovers.
In the final two stanzas, the poet enters into an extended conceit. The two lovers are like saints who are canonized not for holiness, but for love. People will write sonnets, or better yet hymns, about their love. They will be remembered in legend long after they are dead, for love has made them “one another's hermitage.” They have found the whole world in the mirrors of each other's eyes. They have absorbed each other so thoroughly that other lovers will look to them as the highest example and pattern of love.