most substances that are not metals look dull. why? they are not ductile. they are not malleable. they lack…

Brief Explanations:

Luster refers to the way a substance reflects light. Metals have a shiny luster due to their free - moving electrons. Non - metals lack this property of reflecting light well, which makes them look dull. Ductility and malleability are related to a substance's ability to be drawn into wires or hammered into sheets respectively, and are not directly related to the appearance of dullness.

Answer:

They lack luster.