|MadSci Network: Chemistry|
You've asked a really good question, and that question is one that was asked thousands of years ago by the ancient Greeks when they were busy inventing science.
The metals in your home, as well as every other thing in the world, are all made of atoms. An atom is the smallest piece of something you can have. In the case of metals, there are dozens of different kinds of atoms, called "elements", and each atom of any element is identical to any other atom of that element.
Now here's the trick: most of the metal items in your house are actually mixtures (called "alloys") of different metal elements. There's copper, aluminum, iron, and zinc in the wires in your house, there's iron, chrome, manganese, zinc, and carbon (not a metal, but still an element) in your plumbing. Magnets stick to your refrigerator because there's iron in the skin of the door. There's tungsten (element symbol = W) in your light bulbs, and possibly mercury (Hg) in your thermostat.
For your next question, metals are shiny because of the way metals hold their electrons. The electrons are very free to move around, so the electrons are able to absorb many different colors of light. They emit these same colors when the energy leaves the metal, so they appear shiny. Certain metals absorb certain colors, like gold will absorb purple, and reflect more yellow colors and cobalt absorbs orange and appears blue.
Metals are heavy for two reasons. Most metals organize their atoms into a repeating crystal pattern, so the atoms are snug to each other. This increases the density. The other reason is the alloying part of it. We add carbon to iron to make steel, which is stronger than pure iron. This works by putting carbon atoms in the tiny gaps between the iron atoms in the crystal. This increases the density and makes the metal heavier. (By the way, aluminum is not very dense, and it's still a metal. It has a different crystal pattern.)
I hope this helps!
Why Metal is Shiny
Try the links in the MadSci Library for more information on Chemistry.