Máel Coluim mac Donnchad, also known as Malcolm III or Canmore or Long-Neck, was King of the Scots from1058-1093. He was the eldest son of King Duncan I, and he ruled Scotland in the last years of Edward the Confessor’s reign of England and for the entire reign of William the Conqueror. The territory he ruled did not extend over the entirety of modern-day Scotland, as the north and west of the country at that time remained under Scandinavian, Norse-Gael control.
Malcolm’s father, Duncan, began his reign of Scotland in 1034, upon the death of Malcolm II. Duncan’s reign was short, and in August of 1040, Macbeth (Mac Bethad mac Findlaich, the Macbeth of Shakespeare’s famous tragedy) killed him. While Shakespeare depicts Duncan as an old man and Malcolm as an adult, it’s more likely that Duncan was still a young man at the time of his death, and Malcolm was just a child. Malcolm’s family did later attempt to overthrow Macbeth, but they were not successful, and so Malcolm and his younger brother were taken into hiding. It’s believed that Malcolm spent most of Macbeth’s reign under Edward the Confessor.
Some sources say Malcolm killed Macbeth in 1057, and then killed Macbeth’s son Lulach in 1058. Malcolm spent most of his reign maintaining the demarcation line between the kingdoms of England and Scotland. He fought successive wars against England, with some believing the goal of these campaigns was to capture the earldom of Northumbria.
In 1066, Malcolm gave sanctuary to Tostig, the brother of Harold Godwineson, but the king of Scotland did not have any direct role in invading England with Tostig and Harald Hardrada later that year, which ended at the Battle of Stamford Bridge.
In 1068, Malcolm gave exile to Agatha, widow of Edward the Confessor’s nephew Edward the Exile, as well as her children, including Edgard Atheling, and also Gospatric, the Earl of Northumbria. The following year the exiles returned to England and caused trouble for King William yet again.
When a Danish army under the command of Sweyn Estridsson invaded England in that same year, Malcolm chose this opportunity of weakness to invade England himself. He marched south through Cumbria, and he met up with Edgar Atheling. Since little came of the Danish invasion, Malcolm quickly turned back for home, but William sent Gospatric, who had switched allegiances back to William, to raid Scotland. In response, Malcolm raided Gospatric’s lands in Northumbria. These small skirmishes between England and Scotland were common throughout Malcolm’s reign, even though Malcolm did submit to William at Abernathy in 1072.
I will not cover the relationship between Malcolm and William’s son, William Rufus, which was in the later part of Malcolm’s reign.
Skipping to the incident of Malcolm’s death, according to the chroniclers, Robert de Mowbray, the Earl of Northumbria, ambushed Malcolm’s army near Alnwick on November 13, 1093. Reportedly, the steward of Bamburgh Castle, Arkil Morel, killed Malcolm during the battle. Malcolm was taken for burial in Tynemouth Priory, but was later reburied at Dunfermline Abbey, or possibly Iona.
Source: http://en.wikipedia.org/wiki/Malcolm_III_of_Scotland. *Note: the wikipedia article is very detailed with many notes and citing many references. If anyone has any corrections to the material presented, please let me know.