okay, take a deep breath.. Now exhale. Feel calm? Good.
The first thing you want to do is look at metal. Polished metal has reflections. Rusty metal, not so much.
As for how light works, it's really quite simple. There are highlights, midtones and shadows. This is what shading basic objects such as cubes, spheres and cones will teach you. It'll also help you understand the value structures.
As for why some areas have light without the first light hitting the object: This is where reflected light comes in. Just like sound, areas also reflect light. How do you think a mirror works? The light reflects off the shiny surface and into your eye. This does not mean an area has to be a mirror to reflect light.
And again, coming back to metal - you just have to know what type of metal you want to deal with and how the light reacts when it hits that type of metal. Is it polished, rusty, scuffed, gouged? All this will require you to do research. Find references of what kind of metal you're looking for. Study it, and ask yourself "why does this area look the way it looks?".
How long will it take to master this stuff? Depends on how much you study and practice. If you teach yourself, it'll probably take a while. If you have someone who knows this stuff already help you out, you'll probably take it in pretty quick. Not overnight quick, but I'm thinking over maybe a few years? I've been drawing seriously since fourth grade and light was easy to understand - it was technique that took me a while.
Doctors heal you, Artists immortalize you.
"Those who can, do. Those who can't, teach" - bullshit.
The usual staples for anatomy: