Simple:
* Despite his gruff exterior, the old man had a heart of gold.
* She may seem tough, but she has a heart of gold.
With context:
* Although he was a successful businessman, he always remembered where he came from and had a heart of gold.
* Even though she was born into wealth, her heart of gold led her to dedicate her life to helping the less fortunate.
Figurative:
* He may not have much, but he has a heart of gold, always willing to lend a helping hand.
* Beneath her sharp wit and sarcastic humor lies a heart of gold, ready to comfort those in need.
With an action:
* Her heart of gold led her to donate her entire savings to the local animal shelter.
* With a heart of gold, he volunteered countless hours to help build houses for the homeless.
Remember, "heart of gold" is a common phrase that means someone is kind, generous, and compassionate.