Also, PLEASE be aware that because you can find something doing a web search, does not mean you can use it. If you are using something for your personal use then it is not a problem. But if you are creating something for a client and using an image you "borrowed" from the web you are violating someone's copyright. Unless it is creative commons as are the images you find on Wikipedia.
Again depending on your final use you may want to consider a real stock image resource such as Shutterstock.com If you do a search for metallic background you will find a mind boggling 100,162 pages of images. One or two which are probably going to be exactly what you are looking for.
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