You create a 15 ft. cube of statically charged air centered on a point you chose within range.
The cube is visible by occassional cracks of electricity discharging within.

Metal object within the cloud will attrackt discharges of the static electricity.
Any creature that is in contact with a metal object must make a CON-Saving Throw when they enter the cube, start, or end their turn there.
Creatures take 1d8 lightning damage and half as much if they succeed their save.

On a failed save they also lose half their movement. 

If the Metal Object prompting the effect is worn or wielded they roll the save with disadvantage.
An Arrow, even with a metal head, will not count as a metal object for this effect. 

This effect ends, when a creature casts a lightning spell from within the cube, or takes lightning damage from a different source than this spell, or after 1 Minute.
If ended this way, all the remaining electricity will discharge. Any creature within the cube at that point will take 2d6 Lightning Damage
The caster may also elect to end the effect early. 

For every Spell Level above 2nd, the cube grows by 5 ft.