The phrase "I'm as happy as a lark in the sky" is a common expression used to convey feelings of great joy and contentment. However, there are other synonyms that can also be used to describe the same feeling. Some other phrases and expressions that describe happiness and joy include "over the moon," "on cloud nine," "feeling on top of the world," or even "walking on sunshine." These phrases all convey a sense of euphoria and are often used when someone is extremely pleased or excited about something. Ultimately, the important thing is to find the words that best express how you feel and use them to share your happiness with others.