Question

What type of poetic devices does the song have plz help?
Written in graffiti on a bridge in a park
'Do you ever get the feeling that you're missing the mark?'
It's so cold, it's so cold
It's so cold, it's so cold
Written up in marker on a factory sign
'I struggle with the feeling that my life isn't mine'
It's so cold, it's so cold
It's so cold, it's so cold
See the arrow that they shot, trying to tear us apart
Took the fire from my belly and the beat from my heart
Still I won't let go
Still I won't let go
You
Ooohooh
'Cause you do
Oh you, use your heart as a weapon
And it hurt

Answer 1

the second to last line is simile. It's comparing his heart to a weapon.

Answer 2

Repeating the last line of a stanza is standard old time Delta Blues. Almost all of the artists of the 1920' through the 1950' did it in one song or another. Here's a sample by Charlie Patton I surfed up at random.

"I don't want you hangin' round on my job no more"
Fella, down in the country, it almost make you cry
Fella, down in the country, it almost make you cry
(spoken: My God, children!)
Women and children flaggin' freight trains for rides
Carmen got a little six Buick, big six Chevrolet car
Carmen got a little six Buick, little six Chevrolet car
(spoken: My God, what solid power!)


So, I suppose your example is a quatrain (device) and mine is a tercet. That is, if this is right: http://examples.yourdictionary.com/stanza-examples.html