It is possible for a car to be struck by lightning, but the people inside are largely protected from its effects. This is because the car acts like a Faraday Cage.
A Faraday Cage essentially protects everything inside from damage by allowing the lightning to travel around it, rather than through it. So when a car is struck by lightning, the metal frame becomes highly electrified, but the people inside remain safe.
According to the Faraday Cage principle, the total electromagnetic field inside the cage is zero. If there is an electric current, it will conduct around the cage, and because the cage's resistance is low, the objects inside the cage will not be electrified. In fact, a car is one of the safest places to be during a thunderstorm.
However, it is important to note that people in the cabin should not touch anything that is directly connected to the metal frame of the car.
Additionally, lightning strikes can damage the vehicle itself, which can cause a crash effect such as an airbag deployment that could endanger the occupants.
Finally, convertibles or soft-top cars will not have the Faraday Cage effect because they do not have a metal roof overhead.