A refrigerator door?

yup, thats what it looks like to me too.

So, it was not so mysterious ^_^

And what do you think about the photo ?

Nice use of light (you manage to capture the texture of the metal surface with out hot spots) & a nice framing too (the diagonal line adds a lot,separating the frame in two & curves vs lines makes a good combination).Deep DOF (a high f number was used i guess) so all of the details are clearly visible.
Technically correct (imho)

Nope, not a rake...and Thank you!

Its a motorcycle jug. Very nice!

Looks like the edge of an engine block for a motorcycle?

Well Done! Yes...motorcycle block cooling fins...