I understand the frustration people have about the drop rate (I have yet to find a single metal) but deal with it.
Yes the game is free to play but that doesn't make it free to run and operate all those servers. If they decide to give people that help support the game a little boost that seems fair.
If you don't want to pay for metals, don't and don't complain because you're getting the whole thing free.
Don't look a gift horse in the mouth.