The question of whether not employees are able to get benefits when they work part-time depends on the employer. Since benefits are an important and valued feature in the eyes of many employees, it can be beneficial to research a company's policy while applying for work there. Questions about benefits are generally frowned upon during the interview, but if the topic of compensation comes up, you can discuss it, and you can also ask around among company employees.
In the best case scenario, everyone who works for a company is able to get benefits, regardless of how many hours they put in. However, this is rare, because benefits can be very expensive, and most companies want to cut costs where they can. More commonly, people who work full time get better benefits than those who work part time. For example, all employees might benefit from a company discount, but only full time employees might get retirement benefits.
If you want to get benefits for health care, many companies set up different plans, depending on the amount of hours employees put in. Full time employees might be eligible for more expensive benefits, like dental and vision, while part time employees might have simpler plans with higher copays or less prescription coverage. In some cases, companies will let employees buy up into a higher benefits package, making better benefits available to those who want to pay for them.
In other instances, you may not get benefits if you work part time. From the company's point of view, it is simply not worth offering benefits to employees who do not work as much, especially in the case of seasonal employees. Some companies actively seek out part time workers for this reason, unfortunately, in an attempt to cut costs. However, if you prove to be a capable and valuable employee, you may be able to get more hours, potentially working your way up to part time status.
There is no hard and fast rule about which employees get benefits. Many government employers, for example, give benefits to all employees, regardless of status, and some big companies which pride themselves on caring for their employees offer benefits to all, while other big companies view restricted benefits as a cost cutting measure. If you work for a company which only offers benefits to full time employees, it may be worth a try to ask about buying into some or all of the benefits in the plan, as companies often negotiate cheaper rates for health insurance and other benefits, and you would not be able to get these rates on your own.