I know that ArcGIS Server supports WMTS format.
However, when exporting the map from ArcMap to the server the WMTS format (x,y,z) capability is not supported.
Am i missing something?
How are you exporting the map from ArcMap to ArcGIS Server? Are you publishing a map or image service? If you're publishing a cached map or image service, WMTS should be enabled by default. This is explained further in our documentation here.