The metallic character of elements increases as you move down a group and decreases as you move across a period.
In a group, metallic character increases as the atomic size increases, resulting in a weaker attraction between the valence electrons and the nucleus.
In a period, metallic character decreases as the effective nuclear charge increases, making it more difficult to lose electrons.
Thus, the metallic character decreases from K to Be across the period, and increases from Be to Ca down the group.
Therefore, the correct order of metallic character is: \[ \text{K} > \text{Ca} > \text{Be} \]