I will second the rigid tools. I know you mentioned Lowes but if you have a home depot around check out their selection. I've had my 12 volt drill /impact for several years and it has survived shed building and numerous other projects.I will be the first to step in and recommend the rigid combo with free radio! Not sure if they sell that a lowes but I went to home depot and got the impact driver, drill, 2 batteries and free radio with carrying case for $180. It has been worth every penny. I love the rigid because it comes with a lifetime service agreement at no charge. I did not understand the big fuss about an impact driver until I started using it. Now I use it at least once a week at home. It has been a game changer.
I actually very rarely use the drill at all anymore. I do use the heck out of the impact driver.
Not sure if you have to pre-drill those sheetmetal screws or not, but if not you can probably just get by with the impact. and if they are just small screws there would be no reason to get an 18v driver. The milwaukee M12 is good for most jobs these days - or the bosch or Makita equivalent.

I've been shopping for cordless tools lately. as a welder apprentice I will need an impact, drill, and angle grinder. I too have been considering the Milwaukee 18v sets.
I have come to the conclusion that the brushless designs are far superior than the regular. that and to buy the largest Ah batteries that I can afford.
I was tempted to buy the Makita because they have a coffeemaker! LOL!
Ridgid = free batteries for life. Other guys = dead batteries that need replacing in 5 years.
Just sayin'.
All the batteries really come with a lifetime warranty? Do they define lifetime?

Ok narrowed down to Milwaukee m18 and the dewalt dck281d2 which is the best hands down
Stopped by local Sears to get a battery for my old 1/2 drill and 1/2 impact wrench that took NiCad battery had LiIon for 80 but had a drill and impact driver set with 2 batteries and charger for 119 so I got the drill and driver for 40 bucks we will see if I have to go to lowes still and get the other set
Ok narrowed down to Milwaukee m18 and the dewalt dck281d2 which is the best hands down