Is MgcI a molecular covalent compound?

No such substance as 'Mgcl'.

If you mean magnesium chloride, then the formula is 'MgCl2'. Note the number and the capital letters.

All substances, however they combine are molecules; so it is molecular.

However, it is NOT covalent , but IONIC.

Magnesium ionises two electrons to become the cation 'Mg^(2+)'.

Chlorine has electron affinity , and accepts one electron , per atom, to become the chloride anion 'Cl^(-)'.

These ions then combine as

Mg^(2+) + Cl^(-) + Cl^(-) =

Mg^(2+) + 2Cl^(-) = MgCl2.