Ti isn't touted as being the lightest metal out there. Of the metals that you'll find in general use, i.e. the ones that won't explode or kill you, aluminum is the lightest. It's just not that strong. Titanium, however, is strong and relatively light. Because of it's strength, it can be made thinner to accomplish the same goals and aluminum and thus ends up being lighter over all. It's just an awful conductor of heat...about a 10th of aluminum and about half that of iron.