What metaphors are used in Letters to a Young Poet by Rainer Maria Rilke?

In Section V, Letter VII, Rilke's complimentary reference to the sonnet represents a stage of completion for the Young Poet. It is at this point the Young Poet begins to understand and manifest Rilke's guidance. Finally, Rilke's returning a handwritten copy of the sonnet to the Young Poet makes the metaphorical suggestion that the true value of a work of art comes in the way it can be absorbed, understood, and transformed by others without its essence (a distillation of the artist's experience) being changed.