Resistance exercises are a great way to strengthen your muscles and bones, improve muscular endurance, and to help boost your metabolism. There are different types of resistance training programs you can get into like
Weight Training (Free Weights, Machine Weights)
There are Body weight exercises which focuses on using the weight of your body for strengthening. (I tend to incorporate a lot of body weight exercises in my own exercise programs.
There are bands, medicine balls, kettle bells, etc to use for other types of resistance training.
If you are a beginner and want to start lifting, it is a good idea to start on machine weights, so that you can learn how to do different exercises throughout the full range of motion correctly. Body weight exercises are also good if you are taught correctly. For example, when doing a squat or lunge, there is a technique to keep you from injuring yourself.