Titanium is light, strong, and like aluminum, is corrosion resistant by virtue of the formation of an inert oxide layer on the outside. As long as this oxide layer remains intact, a titanium part is very corrosion resistant and will not react to other metals. Thus, grease applied to the titanium threads will prevent galling, which will expose the reactive titanium as this protective oxide layer gets stripped off. Copper anti-seize grease seems to be the go-to product for the titaniums protection and prevents reactions between differing metals. See this article on galling and titanium fasteners