When shooting a concert or other event under theatrical type lighting, I use a single focus point only (usually the center) and use either Evaluative or Center Weighted metering in Aperture mode when shooting wide/normal angle (less than 80mm on a FF body). If the background is dark, as is usually the case, I use about -1 to -2 stops exposure compensation (EC). I tend to shoot in manual mode with the telephoto lens. The key is that regardless of which shooting mode you select, you must keep an eye on the shutter speed (Tv) and Aperture (Av) displayed in the viewfinder for every shot and adjust if necessary.
My general setup is a 24-105mm IS lens on FF body, ISO at around 3200, Av around f/4, Evaluative metering with -2 EC and the single center focus point. (Nikon's "Matrix metering" is a little less consistent than Canon's "evaluative", so if shooting Nikon I would probably go with center-weighted and about -1 EC.) My second body is a Canon 7D (APS-C sized sensor, like your D5100) with a 70-200mm IS lens, ISO at 1600, Av at f/2.8, center weighted metering with -2 EC and the single focus point. My 7D allows me to use the center point for horizontal shots and automatically senses when I go vertical and switches to one of the points near the top of the frame I have selected for portrait orientation. With both bodies I will mix it up some and go from Aperture to Manual exposure as well as from Evaluative to Center weighted metering. Learning your camera's controls well enough to do this on the fly without even pulling your eye off of the viewfinder is paramount!
The IS/VR doesn't help with subject motion, but it does help with the stability of the surface upon which you are standing. Temporary outdoor stages move around a lot, and even on the ground in the media pit, the ground shakes from the energy pumping out of the speakers (don't forget your ear plugs if you want to still have good hearing in a few years). I own the Canon version of the Tamron 17-50mm f/2.8 Di II and used it on my APS-C bodies as my primary normal zoom lens for several years, but with the narrower Av allowed by the higher usable ISO on my FF body I find using IS at f/4 works better for me.
As far as subject motion goes, be very selective about when you open the shutter. A guitarist's hands slow down at the top and bottom of the strumming motion. That split second between moving up and then down is when you can get a clean shot even at moderately slower shutter speed (Tv). The same holds true for a jumping performer: catch them in mid-air just as they stop going up and start coming back down. If the lights are blinking on/off rapidly, time your release when the lights are up - just be sure your metering was also done when the lights were up. Learn to use the back buttons on your camera body to lock in focus and/or exposure, then wait for the next cycle to trip the shutter.
Don't be afraid to take plenty of extra shots! You are stretching your gear's limits to the edge of their capabilities. Just like when shooting sports, there are going to be some shots where focus or exposure is missed. Your client (or fans) don't care if you took 20 or 200 or 2000 shots, as long as the 20 you deliver meet their expectations. That doesn't mean you just "pray and spray", but it does mean you acknowledge that there will be plenty of times when you anticipated the artist zigging left and he zagged right!
And since you have expressed how new you are to photography, I'll remind you to save your files in RAW format so that you have MUCH more latitude to adjust exposure and color temperature variations in post production. And don't expect too much from your gear. While it is true that better gear won't take a better shot for you, it is also true that lesser gear can limit what you can do in challenging light. You are going to need to shoot RAW at higher ISO and deal with the noise in post. And regardless of your gear, you're not going to get results at a live concert that are as good from a technical standpoint as you would be able to produce in a controlled studio setting.
Canon 5DII, EF 24-105mm f/4 L IS @ 55mm, Aperture Priority, 1/160 sec, f/4, Evaluative metering, -1 1/3 EC, ISO 2000. Exposure increased 0.5 stops in post. At this slower Tv, timing his arm at the top of its motion was the only way to freeze it.
Canon 7D, EF 70-200mm f/2.8 L IS II @ 200mm, Aperture Priority, 1/1600 sec, f/2.8, Center-Weighted Avg., -2 EC, ISO 3200, Exposure increased 0.3 stops in post. I could have gotten away with a stop less ISO and Tv in this one, but even with the noise reduction (NR) needed for ISO 3200 on the 7D, you can still read the numbers and see the index marks on his watch before downsizing! Yes, it is a $2,300 lens.
