Arthur Weasley's youngest son Ron is one of Harry Potter's best friends. Harry and his other best friend Hermione Granger enjoy spending time with the Weasley family and they seem to have been accepted as unofficial members of it.
In Harry Potter and the Order of the Phoenix, Mr. Weasley is a member of the Order of the Phoenix and is attacked by a snake being controlled by Voldemort. Harry, who is mentally connected with Voldemort, manages to see this in a dream and is able to warn the Hogwarts authorities and Mr. Weasley is saved just in time and sent to St. Mungo's Hospital for Magical Maladies and Injuries
The name Arthur Weasley is reminiscent of the birth name of Arthur Wesley, better known in later life as Arthur Wellesley, 1st Duke of Wellington, though at this point in the story it is difficult to know if he will be a similarly heroic figure.