A lot of cats new to brushing will bite the brush if they can't move away from it. The sensation is overstimulating and, in the case of matted fur, can either pull or scratch unseen hotspots or sores caused by matting. Keeping a similar or identical one for them to gnaw on while you work can help them work their frustration with the sensation out, as well as going slow and taking lots of breaks for praise, love, and affection.
Generally, introduce them to the brush slowly and with the right attitude. One cat behaviorist I once followed used to say, "If you're not in the mood to do it, your cat won't be, either." Use positive reinforcement, praise in a soft voice, and treats if possible to very gradually acquaint them with what the brush feels like. Don't try to just brush right away; try pinching a section of hair between your fingers firmly and lightly brushing the ends, so any snags or tugs the cat can barely feel thanks to your fingers holding the strands. That can help acclimate them to having the brush within touching-distance.
If they like to be scratched, distract them with a toy or treat while scratching them like normal, and try sneaking in a few gentle touches from the brush to help them associate the pleasure of scritchies with how nice it can feel to be brushed. I have a long-haired Maine Coon mix that loves her brushies (except around her rear end, which I just have to burrito her and trim with an ultra-quiet cat hair trimmer to save her stress). She first began enjoying brush-time because her favorite place to be scratched is along the side of her cheek and under her chin when she naturally scrubs her head. I just snuck the brush in when she'd start to really get into being pet and scent-marking, and she eventually figured out that it felt really nice to rub her cheek against the bristles. Plenty of patience, positive energy and praise, and consistent repetition in a safe environment were the major keys to getting her happy to see her brush every week/whenever she needs it. Incorporating the brush in with petting/snuggle time can help a lot :)