The use of symbolism to enhance poetry

Read " a valediction: forbidding mourning" by Donne, "The road not taken" by Frost, "Titanic" by Slavitt, "the lamb" by Blake, "la belle dame sans merci" by keats, "Easter wings" by Herbert, "To Celia" by Jonson, "The hand that sign the paper" by Thomas, "to the virgins" by Herrick, "to his coy mistress" by Marvell. EXPLAIN HOW SYMBOLS ENHANCES POETRY, USING ELEMENTS IN THREE OF THESE POEMS AS EXAMPLE.