For light and heat:
* Radiant
* Incandescent
* Luminous
* Beaming
* Shining
* Brilliant
* Resplendent
* Effulgent
* Gleaming
For figurative meaning (e.g., a positive feeling or appearance):
* Radiant
* Beaming
* Effervescent
* Jubilant
* Thriving
* Flourishing
* Exuberant
* Rhapsodic
* Euphoric
For describing skin:
* Healthy
* Rosy
* Vibrant
* Fresh
* Dewy
* Radiant
For describing a metaphorical light:
* Bright
* Vivid
* Warm
* Inspiring
* Energetic
* Passionate
The best synonym will depend on the specific situation and the nuance you want to convey.