Umm, STLs oversee all aspects of the store. So, any metric that Target deems necessary to measure is ultimately the STL's responsibility to meet (in the eyes of the DTL and above). Some metrics get more focus than others, and that can change from year to year depending on district, group, region, and corporate goals. For instance, REDcards used to be a huge metric for our store, but over the last year, the DTL has stopped being so focused on them and is now more concerned with myCheckout sales and A/A performance. All that said, sales and payroll are always going to be two big ones that fall on the STL to meet.
Are you still in college? If so, you're going to need to finish your degree before you're able to get an ETL position. Consider applying for the Executive Intern program if you're still in school. That would be a good first step. If you don't have a 4-year degree, it's going to be very difficult getting an ETL position without first being a TL for a few years prior and doing well in that role.
Once you land an ETL position, you will need to do that for about 3-5 years before being considered for an STL role.
All of this assumes you have no prior retail management experience, at Target or elsewhere. If you do, then the career path to becoming an STL could be shorter for you.