Original: When I was younger, I played in a rock band and painted!
Corrected (natural): When I was younger, I played in a rock band and painted.
Other clear alternatives:
- When I was younger, I used to play in a rock band and paint.
- When I was younger, I played in a rock band and painted pictures.
Explanation:
- The original sentence is grammatically acceptable: the verbs are parallel and both in the past tense.
- Consider removing the exclamation mark unless you want an emphatic or excited tone; a period is more neutral.
- If you want to be more specific, add an object to "painted" (for example, "painted pictures" or "painted murals").