a reason metaphor is an effective literary device?

a reason metaphor is an effective literary device?
I’m writing my response to literature essay for the poem “mother to son” and I need a good reason metaphor is an effective literary device. here is the poem by Langsten Hughes.. “…Well son i’ll tell you
life for me ain’t been no crystal stair
it’s had tacks in it
and splinters
and boards torn up
and places with no carpets on the floor

but all the time
i’se still been climbin’ on
and reaching landin’s
and turning corners
and sometimes going on in the dark
where there ain’t been no light
So, boy, don’t you step down on the steps
’cause you find it’s kinder hard
don’t you fall now
for i’se still goin’, honey,
i’se stilll climbin’
and life for me ain’t been
no crystal stair…”

The “crystal stair” represents an easy life, with all the way smooth and clear for you to just waltz on up it. When the mother begins to tell her son about how the “stairs of life” have been for her, she describes a dilapidated, dangerous staircase. Evidently, her life hasn’t been too easy: she’s had to climb on up carefully, avoiding the tacks and splinters. This metaphor effectively shows what she’s trying to say. Has your english teacher ever told you “show, don’t tell”? A metaphor is a great way to do just that; it proves a point so much more clearly and beautifully than if the mother had just said “my life is hard.” The metaphor in this poem provides description of exactly *how* hard her life has been.
Please don’t just copy this for your homework; it’s only meant to be an idea.