To eat like a bird/horse simile
If you say that someone eats like a bird, you mean that they eat very little amount of food.
She is seriously ill, so currently she can only eat like a bird
Despite eating like a bird, she is overweight.
She seldom does exercise, so she eats like a bird.
2. If you say that someone eats like a horse, you mean that they consume a large amount of food.
Barry, one of my bosom friends, is about to drop in on us, let's prepare a gargantuan meal as this man eats like a horse.
I admire those who look skinny yet they can eat like a horse.
After working out, he often eats like a horse.
To devour.
The verb "eat" must be conjugated according to its tense.
To eat like a bird dates from the first half of the 1900s, alludes to the misconception that birds don't eat much (they do, according to their size). Eat like a horse is an antonym that dates back to the early 1700s and refers to horses' proclivity to eat whatever food is available.
To do domething based on your emotions rather than for rational reasons
I can't believe that Tom beat his classmate. He's always the one who let his heart rule his head.