Can I use this type of board for walls and roof and floors for my shed if I intend to cover the exterior in sheetmetal?. if so, should I paint all of the OS.. just in case it rains while I'm building?. this is going to be a 1 man job so its going to take me awhile.. thanks for any help

You can use OSB for everything. This sheathing is now the most used sheathing today.
If the job will take you awhile you can spray some Thompson's waterproofing on any of the exposed sheathing.
In case your wondering, shinny side down on the floor and roof and "in" when applying it for the walls. Rough side w/ the lines to be exposed.

With the lines?? I thought OSB looked like flakes glued together?

There are paint lines on the rough side of the OSB every 16" & 24". They are so you know where to nail if you installed your framing correctly. Example... 16" o.c. or 24" o.c.
That's what I meant by lines.
Your correct w/ the OSB looking like glued flakes. OSB- oriented strand board

I need to save $$ on my little shed.. its OK?? To space my wall studs 24" then?

Sure you can go 24" o.c. Use 2x4's if you do. You can also use 2x3's and go 16" o.c.
I'd personally use 2x3 16" o.c. for the walls then 2x4's 24" o.c. for the roof.

can i use this type of board for walls and roof and floors for my shed if i intend to cover the exterior in sheetmetal?...if so, should i paint all of the OS..just incase it rains while im building?...this is gonna be a 1 man job so its gonna take me awhile..thanks for any help
Cover it with tyvek or any other housewrap

Use

Use 7/16 osb nothing thinner Julie