Are you looking for 200ft indoors or outdoors?
Will there be obstuctions or will there be unrestricted line of site from point to point?
Let us know
In that case we need to go to the high end of the spectrum of available wireless devices as you have a metal building and some distance to cover.
Your best bet would be to ignore the normal household types of routers and use something like a Bountiful Wireless Router http://www.bhphotovideo.com/c/product/518641-REG/Bountiful_WiFi_BRWG500_BWRG500_Long_Range_Wireless.html#features
This is a unit not a lot of people have heard of, however it is one of the most powerful domestic level routers available in the US and its transmission level is the highest allowed under FCC regulations for domestic wireless devices.
This way you would have a nice solid base station that should penetrate the metal building without the need for additional external antennas or any other devices at the other end other than a standard wireless network card in the computer.
Take a look and let me know if you need more info