Answer:
Physical Properties
Alkali metals are good conductors of heat and electricity while halogens are poor conductors of heat and electricity.
Only specific to Alkali metals: They are soft and can be cut by knife.
Chemical Properties
Alkali metals have 1 valence electron while halogens have 7 valence electrons.
Alkali metals react with non-metals to form ionic compounds while halogens react with non-metals to form covalent compounds.
You can also look at the trends ( melting/boiling point, reactivity) down their group.