Trying to get my mega 2560 to work for my 3d printer
COM4 ... assuming it's a windows host, then?

All those errors may be because the COM port specified doesn't exist. (changed and/or not seen)

0.) Has this mega ever had a sketch uploaded successfully before this? (for anything)

1.) Have you verified within the arduino IDE that COM4 is showing up in the ports menu?  (Tools => Ports)

2.) Did you plug the arduino into a different USB port?  (sometimes when it's re-recognized it'll assign a different COM port)  

If it's changed COM port, then (obviously) change the port designation in the IDE.

Try switching it to a different USB port and waiting for device manager to recognize it.  If that doesn't work and the mega worked before update the question with the above info and we'll try again.