The correct order of the metallic character of the elements Be , Al , Na , K is

Metallic character decreases as we move across a period in the periodic table from left to right. This occurs as atoms more readily accept electrons to fill a valence shell than lose them to remove the unfilled shell. Metallic character increases as we move down an element group in the periodic table.

Potassium belongs to 4th period, sodium and aluminium belong to 3rd period, beryllium belongs to 2nd period in the periodic table. Hence, their correct metallic character is $\mathrm{K}>\mathrm{Na}>\mathrm{Al}>\mathrm{Be}$.