Yes, the phrase "my brother is as fast as lightning" is a simile because it uses "as" to compare your brother's speed to that of lightning. It can also be considered a hyperbole, as it exaggerates his speed for emphasis, suggesting he is extremely fast beyond normal human capabilities.
He ran as fast as lightning
as fast as lightning or as fast as light
An example of a simile is, 'The girl was slow as molasses.'
It is a simile, they use like or as. Like many similes, you could convert it to a metaphor: "In the ring, his hands became bolts of lightning."
Two shakes of a lamb's tail.
cheetah
I can finish my homework! (pretty slow)
personification- the trees danced in the wind smile- her cheeks were as res as a cherry metaphor- i don't know hyperbole- i text so fast i can text 20 words in a second
as fast as a cheetah running from extinction
As quick as a flash, she raced across the meadow.
There are two usual similes, one animal, one object:As swift as an eagleAs swift as an arrow*The corresponding simile, even more extreme, is as fast as lightning.
he ran as fast as a cheetah << everyone knows thatt -- a better one may be he/she is as quick as lightning OR he/she is as fast as a bullet