What is this Device Called, if it is one at all?

I wrote a poem inspired by  a relationship I was uncertain of.  In the poem, I connected a few metaphores; with a twist:

"...not even the beautiful stars seem to help.
They shine and they twinkle,
but they're as cold, and as sharp
as the edge of this road,
And that knife in your hand
is your heart on the lamb..."
This is the metaphorical device I'm wondering about.  This connection I made with  the "edge" of the road being cold and sharp like the knife... in actuality the knife is a metaphore, but the edge of the road is actual.
Also, the "Is your heart on the lamb" is as much a question as it is a fear.

The poem starts out:  "Walking this lonely highway again"

I'm saying the knife is the girls reluctance to be anyone's. 
"on the lamb" is what prison escapees are... they are running from captivity.
The poem continues:

"or is your heart dwawn closer to a past;
hoping for a day that may never come,
but keeping me just in case."

Tell me your thoughts.  Leave a comment.

Beethoven Symphony No. 5, 3rd mvt--Arturo Toscanini/NBC Symp

This is so good that I wasirrestably compelled to post it here... so good! Bravo!