As autotech has stated this motherboard has support for 1600MHz & 1333MHz modules.
This is shown on the Gigabyte QVL (Qualified Vendors List) of supported modules check here:
http://download.gigabyte.eu/FileList/Memory/mb_memory_ga-b85m-d3h.pdf This list shows which modules have been tested and approved by Gigabyte but I have to say from my own experiences that it is not definitive and modules not on the list may also work OK at the rated speeds of 1600MHz and 13333MHz. If you wish to run RAM modules faster than 1600MHz then you are really entering the realms of O/C'ing on this board.
That said, you may be able to get the RAM to run at its rated speed but this will involve manually setting things up in BIOS. The first thing to try would be to load the XMP settings and see if the system will POST/BOOT, if it does great. If it doesn't, then you will need to switch the Memory Settings to manual and probably tweak them to get things to run.
The difference in real time performance of 1866MHz RAM and 1600MHz is probably not that noticeable and in my opinion it is probably not worth the hassle trying to get these modules to run at the faster speed.