What kind of substance has properties that reflects light very well, warms up in my hand, flattens out when it hits with a hammer and conducts electricity?

a metal?

Based on the properties you described, the substance you are referring to is likely a metal. Metals have unique characteristics that make them stand out from other materials. Let's break down the properties you mentioned and explain why metals possess them:

1. Reflects light very well: Metals are known for their high reflectivity. This property is due to the presence of free electrons in the metal's atomic structure. When light hits a metal surface, these free electrons absorb and re-emit the light, resulting in high reflectance.

2. Warms up in your hand: Metals are good conductors of heat. When you touch a metal object, such as a metal spoon or key, heat is transferred from your body to the metal due to its high thermal conductivity. This transfer of heat makes the metal feel warm in your hand.

3. Flattens out when struck with a hammer: This property is related to the malleability of metals. Metals, in general, have the ability to deform under external forces without breaking. When struck with a hammer, the metal's crystalline structure allows it to absorb and distribute the force, resulting in a flattened shape without fracturing.

4. Conducts electricity: Metals are excellent conductors of electricity. This is again due to the presence of free electrons within the metal's structure. These free electrons are able to move through the metal lattice, creating a pathway for electric current to flow.

To summarize, the substance you are referring to possesses all these properties because it is a metal. Metals have unique atomic and crystalline structures that enable them to reflect light, conduct heat and electricity, and exhibit malleability.