Finger Lightning

You channel your inner energy and shoot lightning from yourself at a creature or an object within range. The target rolls a Dexterity saving throw and takes 1d10 lightning damage on a fail. If the target is made (for example an Iron Golem etc.) or wears armor made of metal (for example a Chain Shirt, Plate Armor etc.), it has disadvantage on the saving throw.

You may additionally do ONLY one of the following:

Upcast: You can expend a spell slot and add +1 damage dice per spell slot level (Level 1 +1 damage dice, Level 2 +2 damage dice .... Level 9 +9 damage dice.)
Hold concentration: When you hit with this cantrip not upcasted, you can choose to hold concentration to impose disadvantage on attack rolls for the enemy that got hit until the end of the enemies next turn. However, by doing so you cannot use any other actions (including bonus + free actions), reactions and your movement speed is limited to 15 feet while concentrating on upholding the stream of lightning. You are still able to move. Each round, the target must roll another Dexterity save and either recieve damage and disadvantage on a fail or nothing on a success.

You can freely decide the color of the lightning.

Cantrip Upgrade. The damage increases by 1d10 when you reach 5th level (2d10), 11th level (3d10) and 17th level (4d10).

Creators Note: This spell may is called "Finger" Lightning but it does not have to be shot out of fingers the classical way. Technically, you can shoot it out of your eyes, mouth, your behind, feet or even ear. Whatever you think is fancy no matter what you wear :D

"Uuuuuunlimiteeeeed POWAAAAAAAAAHHH!" -A Black Robed, Evil Space Wizard