I have to find poetic devices in the song Titanium by David Guetta for school, and I was wondering: You shout it outBut I can't hear a word you sayIs...

This line is
certainly paradoxical because it seems contradictory. One person shouts but the other cannot
hear it. This is also an example of situational . This is when the desired effect is the
opposite of what one might expect. A shout is expected to be heard. When it is not, it is
ironic. In this song, the speaker might actually hear the shouts/criticisms, but he/she chooses
to ignore them. So the notion that he/she can't hear is metaphoric. 

In the
rest of the song, the speaker usesto explain the power of those criticisms and his/her
resistance to them. The bullets are metaphors for the shouts/criticisms. The speaker is like
titanium, which is a low-density but very strong transition metal. In other words, even though
he appears vulnerable (low density), he is highly resilient. One could argue that the bullet
metaphor is an example of(an exaggeration). Criticisms are described as bullets to illustrate
their destructive power.