Hi and welcome to POTN,
gjl711 wrote in post #15654658
yes, it will work fine. As long as it has a ed
or ef-s mount it will work.
JJ meant to say EF or EF-S mount. That particular lens will have an EF mount (if, in fact, it's made to fit Canon... Sigma also makes lenses to fit Nikon, Sony, Pentax and their own Sigma cameras). If it says "Canon" or "Canon AF" on it, it'll work fine.
However, Nekrosoft13 is also correct... the 50-500mm quite likely is not a very good choice of lens for indoor shooting. It might give you the telephoto reach you need, but it's too small an aperture for use in a lot of (most?) indoor venues. You'll have to bump up the camera's ISO as high as you can before images get too noisy (probably ISO 1600 to 3200 on a 550D)... and even then you will be using marginal shutter speeds to photograph moving subjects. Also, the 50-500mm is nicknamed the "Bigma" for a reason. It's a large, heavy lens. You'll likely want a tripod, or at least a monopod to use with it. You won't want to handhold it very long. It's about twice the weight of the 70-200/2.8 or 300/4 IS that I use.
First, you need to get closer to your subject. Next, due to the lighting indoors, you likely will need f4 or even f2.8 lenses. Those are bigger and more expensive. The strong telephotos are very, very expensive. (Look up the price for a Canon 400/2.8 IS, for example.)
A versatile lens you might find adequate is the Sigma 120-300/2.8 OS. Attach a quality 1.4X teleconverter and it will act as an 168-420mm f4 lens. That combo will cost about $3500 U.S... and that's about the cheapest option for a versatile zoom setup.
A 70-200/2.8 is unlilkely to be long enough telephoto, since your 55-250 is not enough. With a 70-200/2.8 you can add a 1.4X teleconverter, but that only gets you a 112-280mm f4 equivalent. There are 2X teleconverters that would make it a 140-400mm f5.6, but the only lens where there wouldn't be a hard hit on image quality is the Canon 70-200/2.8 IS Mark II paired up with the EF 2X Mark III teleconverter... a combo that would cost about $2600 U.S. (at current sale prices, it will be closer to $3000 when those expire at the end of March, here in the U.S.) There are other Canon, Tamron and Sigma 70-200/2.8s... All are real "workhorse" lenses, designed for professional use, with fast focus and high image quality. But, again, they don't have as much reach as your 55-250mm, so if that lens is too short, the 70-200 alone will not be as good. Besides the combo mentioned above, a 1.4X teleconverter is the strongest I'd use on any of the other models.... and that only gets you the equiv. of 280mm, only slightly more reach than your 55-250mm
A somewhat more affordable option, I use a Canon 300/4 IS a lot, both with and without teleconverter. With a 1.4X on it, it's equal to a 420mm f5.6. This is handholdable, but really pushing your luck with adequate light indoors. The lens sells new for $1450 and a good, but affordable third party teleconverter such as the Kenko MC4 1.4X DGX sells for about $150. You might find the 300/4 IS used... it's been around for a lot of years... for a bit less money. I paid $900 for a very lightly used one and have occasionally seen them for $850 U.S.
Sigma does make a 200-500mm f2.8 lens... Plenty fast for indoor shooting, but it's rather huge and costs $26,000 U.S.
Using ISO 3200 on your camera, you may want to get noise reduction software such as Noiseware from Imagenomic.
It ain't cheap to get good shots at events... if it were, everyone would do it themselves.