The Living Dead series by George A. Romero. All classic films.
"They're coming to get you, Barbara!"
Night of the Living Dead. Bickering siblings Johnny and Barbara drive to a rural Pennsylvania cemetery to place a cross with flowers on their father's grave. There, they notice a dead man walking towards them, who suddenly attacks Johnny. Barbara flees and ends up finding a man who can provide some protection and aid. They must do their best to survive the crisis, an age where the dead have awaken to feed upon the living.
Dawn of the Dead. Following the scenario set up in the previous movie, the film depicts the United States of America struck by a pandemic of reanimated zombies, who now have no other desire than to feast on the flesh of the living. Some workers at a local television studio in Philadelphia manage to escape the crisis around them by helicopter, but only for a while. They end up finding other human resources to aid them, and enter a mall which is plagued by zombies but loaded with essential supplies to survive as well. Can they manage to avoid the zombies and steal enough supplies to survive?
Day of the Dead. An undead apocalypse has ravaged the Earth whilst America's last surviving humans study them from within an underground military establishment. The survivors are horrified at the prospect that they "are the only ones left", creating a crisis within human civilization over whether or not the idea of human society should be continued or abandoned. The scientists have been ordered to find a resolution to the epidemic but are tempted to violate nature's boundaries guarding life and death, soldiers who are assigned to protect the doctors appointed to study the zombies but are tempted to enforce fascistic martial law and destroy the specimens in an act of rebellion, and the civilians who are assigned to serve both groups with necessary services like transportation and communication are tempted to abandon the cause as well.