You have advantage on this attack if the target is wearing metal or made of metal.

Melee Spell Attack

• Hit: 1d10 electric damage,* and the target cannot use reactions.

*At Higher Levels: This spell's damage increases by 1d10 when you reach a total character or creature level of 5th level (2d10), 11th level (3d10), and 17th level (4d10).

If for some reason your target is wearing or made of non-conductive metal, like lead or titanium, you do not have advantage on the attack roll.