What metaphor does the poet use in lines three and four of the poem, Kindness?

Instead of explaining what the opening lines mean right away, the speaker relies on an intriguing metaphor to make the point. (A metaphor is a figure of speech that compares an intended concept or thing to something unrelated as a way to clarify the original intention.) The speaker wants to describe how the future can "dissolve in a moment," so she compares it to "salt" dissolving "in a weakened broth." The notion of losing all of one's tomorrows is a frightening prospect, and likening it to something as easy as salt blending into soup makes it all the more chilling. The first thing "you must lose" to know true kindness, then, is a hefty loss indeed.