Which property of metals makes them appear shiny? 

Metallic  lustre 

The correct answer is option 2. Metallic lustre.

The property of metals that makes them appear shiny is metallic lustre. Metallic lustre refers to the shiny appearance exhibited by metals when they are polished or freshly cut. This property arises due to the presence of free electrons in the metal's structure, which can move freely and interact with light. When light strikes the surface of a metal, these free electrons reflect and scatter the light, giving metals their characteristic shiny appearance. So, the correct answer is Metallic lustre.