How does metallic character change across a period?
Look at the Periodic Table. Most of the elements are metals, i.e. most of the elements are NON-MOLECULAR materials in which the valence electrons are delocalized across the entire lattice such that the bulk material is malleable, and ductile, and TEND to form CATIONS - all metallic properties.
Of course, a few of the elements are non-metallic, and (sometimes) molecular materials, whose higher nuclear charge tends to polarize electron density, giving chemically oxidizing species species - certainly this is true of non-metallic oxygen and fluorine.