Let's start the year with a bit of metallurgical whimsy. After all, materials--their properties and their strengths--are foundational to our efforts here.
There is a company out of Toronto, Ontario that is teaching the world about metallurgy. I don't know if that was their intent or not, but it is a result of their product offering advertisements.
You have seen their ads. The company is called Forever Spin and they are selling toy spinning tops to adults. They appeared on the scene a few months ago with tops made of one metal. Now, they have expanded the line.
You can see all of them
There is quite an education to be had by carefully reviewing this page.
Although no strength of material specifications are given, one can determine the relative weights of metals that one might consider for various applications. One learns, for instance, that titanium is about 60% the weight* of stainless steel. Likewise, copper is about 110% the weight of stainless steel, while magnesium is only 20% the weight of stainless steel.
One also finds nickel has the best surface finish of all the metals presented.
The biggest surprise of all, however, is that tungsten is 210% the weight of stainless steel.
Finally, one can ascertain to a rough degree the costs of the various metals, as they are each priced individually.