Just a guess. You are ..
Some want me high, others low.
If you are on the ground, you will want it high. If you are flying, you want to be above it (low).
But always upwards do I go.
Lightning travels upwards
Quickly or slow, large or small.
different types of discharges, including ball lightning, which can appear to travel slowly.
It is often me you will call.
Call lightning to smite your foes
In the end, I alone decide,
Who is happy, and who will hide.
Some people like thunderstorms, and some try to hide.
Figure it out, don't play around,
Never play in a lightning storm
Hurry, before the applause does sound.
The thunderclap that comes with the lightning.