Which property is common among metals?

Metals are characterized by several distinctive physical properties that set them apart from other classes of elements. One of the most notable properties common among metals is their good thermal conductivity. This means that metals can efficiently transfer heat, making them excellent materials for applications that require heat conduction, such as cooking utensils and heat exchangers. The atomic structure of metals, characterized by a lattice formed by positively charged ions surrounded by a 'sea' of delocalized electrons, facilitates the movement of thermal energy throughout the material.

In contrast, while high electronegativity pertains to how strongly an atom can attract electrons in a bond, metals typically possess low electronegativity, which is why they're more likely to lose electrons than gain them. Brittleness can be more associated with non-metals or certain alloys, as most metals tend to be malleable and ductile, allowing them to deform without breaking. Transparency is not a typical metal property; most metals are opaque because they absorb and reflect light rather than allowing it to pass through.

Thus, the property of good thermal conductivity is a fundamental characteristic that is consistently observed in metals, making it the correct answer.