A bit about meltdown...
Many things can cause meltdowns, such as social demands, frustration, embarrassment, challenges with communication, emotional triggers, sensory build-up, demanding situations, or a combination of these.¹
Meltdowns might look like yelling, stomping your feet, or crying.

This is how some autistic adults describe meltdown...
What are the impacts of meltdowns?
After meltdowns, people often regret things they said or did. You might not clearly remember what happened. Following meltdowns, you might also have feelings of guilt, shame, and embarrassment about the situation.
Some autistic adults find that they don’t experience meltdowns as much as they did when they were children. Others find that they still experience meltdowns often. Some people feel that as they have matured, their meltdowns have been replaced with shutdowns (which are described in a different section).
Watch a video explaining "Autistic Meltdown"...
References
1. Phung, J., Penner, M., Pirlot, C., & Welch, C. (2021). What I Wish You Knew: Insights on Burnout, Inertia, Meltdown, and Shutdown From Autistic Youth. Frontiers in Psychology, 21. https://doi.org/10.3389/fpsyg.2021.741421