As “Reign of Fire” director Rob Bowman says on the DVD, the only way to make a B-movie good is to treat it like an A-movie.

This successful strategy is seen in full bloom in such masterpieces as “Aliens” and “Raiders of the Lost Ark.” While “Reign of Fire” certainly is not up to the par with those films, it is not for lack of trying — and the sincerity of the effort is what makes this a decent movie.

The pigeon-holed plot takes place in a post-apocalyptic future devastated by huge dragons. Small bands of human survivors cling to life in remote, desolate areas, under continual fear of discovery. Quinn, an earnest and intense Christian Bale (“American Psycho”), leads one such group, which is hiding out inside an old English castle.

When the group’s tentative attempts at agriculture are ruined by dragons, all hope seems lost.

Enter Denton Van Zan (Matthew McConaughey, “A Time to Kill”) and the Kentucky Irregulars, a rag-tag group of ex-military types that show up at the castle in a series of tanks and helicopters, claiming to be able to do the impossible — kill the dragons.

Muscles bulging and shaved-head glimmering, Van Zan rolls around the set spewing out kill-the-dragons sentiments with such an intensity of purpose so as to inspire the overly-cautious British group to join the fight. McConaughey’s out-of-nowhere, wild-eyed performance is completely addicting, and it lifts “Reign of Fire” out of the realm of the mediocre.

The admirable action sequences are entertaining and intense, and the dragons are the most impressive-looking sky-lizards in recent cinema memory. By the end, you will be grinning along as Van Zan finally puts to use the wicked axe he has been lugging around the whole time, in a bad-ass scene celebrating all that is the B-movie.

What fun. Just don’t think too hard about the plot.

The DVD is sparsely populated with special features, but there is a piece on the pyrotechnics of the whole affair, a making-of featurette and an interview with director Rob Bowman.

Coming out Nov. 26: “Men in Black 2,” “Ice Age,” “When in Rome,” “Undisputed.”