Yes insulating your shed will help keep your shed cool in the summer.
You can also add a window air conditioner to the shed to keep it cool if you're doing work in it during the summertime.
If you plan to put a bed in it to make it an additional house such as a guest house or guest bedroom for someone to sleep in then adding insulation to the shed helps keep it cool in the summer and warm in the winter.
A good natural gas heater or propane heater is good to heat up a shed in the winter and the window air conditioner or a mini split air conditioner can help keep your shed cool in the summer.
The proper insulation for your area will do wonders to keep the shed cool in the summer and warm in the winter.
Just make sure you add enough of the correct R Value insulation as if you do not then it won't work as good.