Which of the following best describes the physical properties of metals?

The description of metals is best captured by high malleability and thermal conductivity. Metals are known for their ability to be deformed under stress without breaking, which is referred to as malleability. This property allows metals to be shaped into thin sheets or wires. Additionally, metals are excellent conductors of heat, which is why they are widely used in electrical wiring and cooking utensils.

Their physical structure includes a lattice arrangement of atoms that enables the free movement of delocalized electrons. This electron mobility not only facilitates electrical conductivity but also allows for efficient heat transfer.

The other options present characteristics that do not align with typical metallic behavior. For instance, metals generally have high melting points and are not considered poor conductors of heat or electricity. They also tend to have a shiny appearance rather than a dull one, contrary to being brittle. Furthermore, metals are solids at room temperature, with very few exceptions, and do not form gases easily under these conditions. Thus, the choice highlighting high malleability and thermal conductivity accurately reflects the essential physical properties that define metals.