Another word that translates as lightning is lampo. Whereas fulmine refers to the occurrence of a natural electrical discharge between a cloud and the ground or within a cloud (or in simpler terms, a lightning bolt), lampo is the bright flash of light produced from the discharge of the bolt (a flash of lightning).
Sono stato travolto da un grosso temporale con tuoni e fulmini mentre tornavo a casa.
I got caught in a big thunderstorm with thunder and lightning while I was heading home.
Two additional synonyms for fulmine are saetta and folgore, although they aren’t used as frequently.
A person or thing that is extremely quick can be metaphorically referred to as un fulmine (a lightning bolt) in Italian, just as we can say as quick as lightning in English.
Quel corridore è veloce come un fulmine.
That runner is as quick as lightning.
If you see someone across the room and fall in love with them at first sight, you could blame it on a colpo di fulmine (lit: a lightning strike).
Tra me e la mia ragazza è stato un colpo di fulmine.
My girlfriend and I fell in love at first sight.
English and Italian both have the figurative expression a bolt from the blue or un fulmine al cielo sereno (lit: a lightning bolt in the clear blue sky). It is a metaphor for a sudden or unexpected event, with reference to the extreme unlikelihood of a lightning bolt appearing on a sunny day.
Fulmine di guerra (lit: lightning of war) is a complementary expression that describes a person who operates in a rapid and decisive manner, or makes decisions and acts upon them quickly. However it is frequently used in an ironic sense to mean exactly the contrary (i.e. someone who is slow on the uptake).
Mi domando se quel fulmine di guerra di Luca ha capito che cosa sta succedendo.
I wonder if that bonehead Luca realises what is happening.
Finally, fulmine can be used in a figurative way to describe anger or fury.
I suoi occhi lanciavano fuoco e fulmini.
His/her eyes were full of anger.