General speed:
* Like a bat out of hell: This idiom implies extreme and uncontrolled speed.
* Like a shot: This idiom emphasizes a sudden and swift movement.
* At lightning speed: This idiom emphasizes extreme speed, often used to describe technological advancements.
* In a flash: This idiom emphasizes the brevity of the speed, like something happening quickly and disappearing just as fast.
* At breakneck speed: This idiom implies dangerous speed.
* Like greased lightning: This idiom emphasizes effortless and smooth speed.
Other nuances:
* In the blink of an eye: This idiom emphasizes the speed of something happening very quickly, almost imperceptibly.
* At a snail's pace: This idiom ironically means the opposite of very fast; it means very slow.
The best idiom to use will depend on the specific context and the feeling you want to evoke.