If you dont have access to a welder but can get a propane torch you can fill the holes with lead.You will need to acess the back side of the holes to back em up with foil tape though.Then you have to have clean bare steel around each hole(on the out side)Its easier to mig the holes shut though with a mig welder.
any good body shop will do it for you ,,, and do it right ,,if you don't know what you are doing you will ruin the panels ,
You need to back up the holes with a copper backer...If you are really good you can just buzz the holes shut with a series of small tag welds till you fill the hole in.The copper backer is used because the steel welding wire wont stick to the copper.It will however conduct heat/electricity.To fill a hole useing a backer...You simply strike a bead on the copper backer creating a molten puddle of steel.You manipulate the puddle till it fills the hole,then you stop...move on to the next one.Note! It is very easy to simply make a bigger hole if you dont know what you are doing with a mig welder.
Its not hard to do. My son and I with very minimal experience closed our holes . Tip: take a peice of body metal and drill a few holes in it and practice first. Start on what ever edge its confortable for your movement and weld a circle filling in the hole. Then as soon as its full use a wet rag and cool the weld it will shrink the weld thus minimizing the grind process. be sure and shrink the weld it will be so much easier to fill. need a mig welder preferable with gas, a bucket of water with rag, and a little patients with positive attitude and you can do this. Remember practice first it wont take long to figure out. my son is 15 and welded most of the holes while I watched,took him about 15 mins. to figure it out. I sure like it when he does most of the work! Good boy
I used 6 penny nails. put the nail in from the back side and weld them in. the nail makes a handy handle and and allows you to handle the job more easily. (3 handles in 1 sentence) cool thing is the car looks like a porkypine before you cut off the nails lol