Step 1: Recall what makes a material conduct electricity well.
A material conducts current easily only if it has a large number of free electrons that can move about within it under an electric field.
Step 2: Think about which materials have such free electrons.
Metals are held together by metallic bonding, where the outer electrons are not tied to any one atom and can drift freely through the whole structure, this makes every metal a naturally good conductor.
Step 3: Check the given options against this idea.
Glass, wood, plastic, rubber, paper, air, diamond, ebonite and brick are all non metals with tightly bound electrons and behave as insulators, while silver, copper and iron are metals with plenty of free electrons available for conduction.
Step 4: Pick the correct group.
Only the group made entirely of metals fits the description of good conductors.
\[ \boxed{\text{Silver, Copper, Iron}} \]