Yes it is safe to microwave Styrofoam Containers.
Styrofoam Containers are microwaveable and as long as you don't microwave the Styrofoam container too long then it will not or should not melt.
I have however before left a Styrofoam container in the microwave too long and it melted some but as long you just put the Styrofoam container in the microwave for only a minute or two to heat the food back up then it should be fine.
You can also microwave Styrofoam Cups to heat coffee and other drinks up as well.
You can heat coffee up in a Styrofoam cup in the microwave.
Styrofoam cups are microwave safe and you can place them in the microwave and heat up coffee, water, hot chocolate etc.
I've been microwaving Styrofoam cups for years now and never had one melt.
You can also microwave those Styrofoam food containers to reheat food in as I've done it several times before as well.
Just don't put gasoline in a Styrofoam cup as the gasoline will melt the Styrofoam cup.
However microwaving Styrofoam cups and Styrofoam food containers is safe and never have I had an issue doing so.