Here is your answer:
Metaphor compare something but it not using like or as.
Example: Tims a giant!
Their comparing Tim to a giant.
Its great to use in poems because it helps you compare your love for something to something else.
Symbols are used as the main idea or theme of a poem.
Example: I leave my heart with her knowing I will never see her again.
The symbol or theme is love!
Its good to use symbols in poems because it helps you to get the main idea of the poem!