Titanium

I figured it'd be a matter of time until this one was stuck in my head. When I went and saw Pitch Perfect, one of the most unnecessarily awkward scenes involved this fantastic a capella duet of a segment of it and I loved it. I don't really get the music video for the song, but I still love the music. AND there are a bunch of really awesome covers for the song. My favorite is of course the one by the piano guys.
So the song is one long comparison to being as stone-hard as titanium. I decided to do a bit of research about how hard titanium really is. It turns out that Guetta did his research (or just got lucky that the societal perception of titanium is pretty close to the truth). Titanium really is an incredibly strong metal- about as strong as some steels while being almost half as dense. We've really only been figuring out what we can do with titanium since the 50s, but it's already a staple in everything from airplanes, medical implants, computers,  and firearms to paints, piercings and fireworks. It might be super expensive to make, but its lightness and strength have generally been deemed worth the cost.
One of the ways in which titanium is so much better than anything else we've got is the layer of oxide that it forms when exposed to air. So, quick chemistry recap (sorry, I'm a nerd, I know) goes like this: They mill the metal and do all the fashioning of it that they need to (see, I'm being nice and skipping over like half a dozen super-cool chemistry steps right there) but as soon as they cut it and new metal is exposed to air, the oxygen in the air starts attacking it (when you make a bar of iron, that's what makes the rust). The big deal is that the layer of oxygenated (=oxidized) metal is generally about 1-2nm thick (~8000x thinner than a hair). That means that the insides of the metal (where all the strength is) don't get affected by the environment.
In one of my classes this week, we talked about putting on armor. My teacher (who was a police officer in California for like 30 years) told us a bunch of stories about officers whose lives were saved by wearing armor (or not saved when they took it off). I remember thinking that it was kind of scary how much of you is still exposed even when you are wearing full body armor. Wouldn't it be awesome if there was a way to be completely coated in armor instead.
I feel like each of us has the chance to decide what we're going to be. Everyone gets exposed to the same environment which is going to do its best to wear you down and make you crumble. If you've got yourself a cheaper iron exterior, you'll be able to hold out for a while, but eventually it is going to weaken. On the other hand, a coating of titanium will still get oxidized in the harsh environment, but it'll hold.

Stone-hard as bulletproof glass
You shoot me down but I won't fall
I am titanium