Is Alcl3 covalent? How?

All the elements in a group do not behave in exactly the same way. They show a gradual trend so that for any property, the second member of a group will normally be intermediate between the first and the third member. In your example of group 4, C is nonmetallic whereas the lower members Sn and Pb are quite definitely metals and the middle of the group Si and Ge are intermediate. Beware of general rules like metals combining with non-metals to form ionic lattices. AlCl3 forms a covalent dimer in the vapour phase and SnCl4 is a water sensitive liquid. Al and Sn are clearly metallic in their chemistry and properties though. It is more useful to think of metallic character which the alkali metals have in abundance but groups 6 and 7 have only a little of.