Running is a high-impact activity, which means it strengthens and remakes bones along with muscles.
While lifting helps to strengthen your muscles, running can actually help to strengthen your bones. Your bones need development to help support the muscles you're building. Running is high impact, which means it loads and remakes your bones along with your muscles. For those who may be at risk of having weak bones, running can help improve that.
Running can help with weight loss by burning extra calories. One hour of lifting in the gym can burn around 300 calories, whereas running for an hour can burn twice that. If weight training plateaus happen, giving running a try can help you get over those plateaus to hit your weight loss goals.