Beowulf and the Battle of Maldon are both epic poems written in the Old English language, and the (as far as we know) original manuscripts were both in the possession of a collector of manuscripts named Sir Robert Cotton by the late 17th century. In a fire in his library in 1731 the Beowulf manuscript was slightly damaged, but the manuscript of Maldon was destroyed. Luckily David Casley, the deputy librarian, had made a copy. The Maldon manuscript was already fragmentary, both the opening and closing lines having been lost.
Both stories are written in an epic style, and both commemorate the ideals and virtues of the warlike Germanic tribes which dominated the region. Beowulf was written about 1000, just after the actual Battle of Maldon took place, in August of the year 991. Maldon was a battle between Byrhtnoth and Anlaf, a Viking leader who later united Norway. He was after the gold from the King's Mint near the Blackwater River in Essex.
Interestingly, in addition to the Battle of Maldon being an historical event, there is some evidence that Beowulf may have been related to history also. The burial rites described are similar to the famous Anglo-Saxon burial site at Sutton Hoo, and two characters mentioned in the poem were historic persons. Offa was a name of a 4th century king of the Angles in Europe, and Hengest went to England in 449. In 455 he co-founded the kingdom of Kent. So to summarise, both poems were written in Old English; both manuscripts were collected by Cotton; and both had historic references.