What happens to metallic character across a period?
It tends to decrease (from left to right)
Metallic character is essentially a measure of how readily an atom loses an electron to form a cation (which metals typically do in reactions).
The electron affinity (energy change associated with addition of electron in ground state) of elements decreases from left to right across a period; a simple explanation is that the atoms want to obtain a full valence shell (octet rule), and adding electrons is more favorable for nonmetals rather than metals.
Therefore, nonmetals (right side) would rather gain electrons than lose them, so they have low metallic character. Metals do tend to lose electrons, so they have higher metallic character.