General Cheerfulness:
* As bright as the sun on a summer day.
* Like a bubbling brook, overflowing with joy.
* As contagious as laughter.
* Like a warm hug on a cold day.
* As vibrant as a field of wildflowers.
Enthusiastic Cheer:
* As loud as a roaring crowd at a sporting event.
* Like a firework display, exploding with excitement.
* As energetic as a puppy playing in the park.
* Like a melody that lifts your spirits.
* As spirited as a marching band.
Supportive Cheer:
* As comforting as a familiar embrace.
* Like a beacon of hope in the darkness.
* As strong as a pillar of support.
* Like a gentle breeze that carries you forward.
* As unwavering as a lighthouse in a storm.
Other:
* As refreshing as a cool drink on a hot day.
* Like a sweet melody that fills your heart.
* As uplifting as a soaring bird.
The best simile for cheer depends on the specific context and the feeling you want to evoke.