Requested by headerko. Not that difficult actually. This is the way I do it. There is some free texture sites on the net with nice metal texture photos for download.
cgtextures.com is on of them. They also got some very nice tutorials there with texture creating in mind.
You can also use a digital camera and take your own textures if you have that . I am now combining two textures to get what I want. Download met1 and met2.jpg in this post to try for yourself.
1. Open met1.jpg and met2.jpg in a paint proggy. I'm using Paintshop pro.
2. I have already taken the saturatin down a bit on met1 for you. This is a matter of taste and what you are looking for.
3. Now copy met2 and paste it as a new layer on met1.
4. Select the met2 layer and change the blend mode on the layer to luminance.
5. And thats actually it. It can be that simple. Or you can add another texture to what you already have.
6. Like adding met2a. Be sure to get the met2a on top of the layers and change blend mode to, lets say multiply. The options are many and only imagination is the limit. By combining and changing blend mode and transparency and using the clone brush you can get pretty ok textures.
7.Bellow are the textures I used.