Thank you so much guys for your help !
I see what you mean Roccstar, your edit is indeed "metallic", but what I was trying to convey was a piece of metal with really sharp edges, nothing "smooth" (should have mentioned it), so in my case eishiya's edit will work better for what I'm trying to do.

But I kinda followed your advice on the shading of my skull's outline, I think it looks better.
Anyway here's my thing, I tried not to copy too much but eh sorry

can I say it's finished ?

almost reminds me of a boss from the legend of zelda: a link to the past
It's supposed to be some kind of Pokémon, but that's a great compliment for me since I love that game
