There are two usual similes, one animal, one object:
As swift as an eagle
As swift as an arrow
*The corresponding simile, even more extreme, is as fast as lightning.
A simile for "swift as" could be "swift as a coursing river." This comparison suggests a rapid and continuous flow of movement, emphasizing the speed and agility of the subject being described. The simile creates a vivid image in the reader's mind, highlighting the quick and seamless nature of the action or object.
Personification.
Historically, the simile has been "deaf as a door post". *NOTE: Today, these kinds of comparisons would be seen as rude.
fiddle
mule
As dear as salt
Niagra Falls morning.
...mule."
as blue as sea
my teacher was as surprised as a dog
To complete the simile "as round as," you could say "as round as a basketball" or "as round as the moon." These comparisons evoke clear images of roundness, making the simile relatable and vivid. Other options could include "as round as a globe" or "as round as a coin," depending on the context you want to convey.
To listen like a hawk.