The correct order of metallic character is

The metallic character of an element is defined as the easiness of its atom in losing electrons. According to the modern periodic table, the metallic character of an element decreases while moving from left to right across a period. $\mathrm{K}$ is an alkali metal. For alkaline earth metals, metallic character increases down the group. Hence, the correct order of metallic character is $\mathrm{K}>\mathrm{Ca}>\mathrm{Be}$.