The first 7 seconds of this song, Nightcore - Wrong Side of Heaven, reminds me of a similar intro of a different track, but I cannot recall it.
Do you know any song with intro similar to the one I posted? I remember it was in piano as well.
As mentioned by suraj there is the original by Five Finger Death Punch, but the piano melody also, in my opinion, sounds similar to the intro in Everybody's Fool by Evanescence.
OP found the answer and wrote it in the question. Here it is:
First of all, allow me to thank you for your answers. The one I was looking for is this Helena Paparizou' Teardrops.
I had the exact same feeling with the intro, and I kept thinking Metallica.
I looked for some month kept thinking Metallica. Now I have the song, I keep thinking about whenever I heard the intro. It is in a slower tempo and all, but it is very similar. The song is My Friend Of Misery: for me it was the song kept going on in my head over and over.