Macbeth is a brave and successful warrior as explained to Duncan by the Captain in Act 1, sc. 2. The Captain tells Duncan that Macbeth fought through the enemy soldiers until he came to Macdonwald himself. Then Macbeth killed Macdonwald, cutting him from the navel (belly button) to his chin. After that, Macbeth cut off his enemy's head and put the head on their battlements (essentially, a tall sharpened stick stuck into the ground). The fighting wasn't over yet, though. The Captain tells Duncan that the King of Norway then began an assault with fresh men and supplies. Macbeth was not daunted, however. Macbeth and Banquo both fought the enemy. Ross then tells Duncan that the Thane of Cawdor assisted the King of Norway in battle against Scotland, but Macbeth and Banquo persevered and won. It is clear that Macbeth is brave, determined, and blood-thirsty in battle. These qualities are seen later when he has becomes determined to hold onto his crown, especially in Act 5.
In Act I, Scene II a captain provides an eyewitness view of a battle between King Duncan's forces and Macdonwald, a treacherous noble, aided by the Norwegian king.
According to his testimony, the battle stagnated for some time. It was hard to tell if Duncan's men would succeed or not. Macdonwald had lots of support from Irish and Scottish foot soldiers and cavalry and appeared very confident on the battlefield. For a while, it seemed as though he had luck on his side.
Macbeth, however, was able to overcome Macdonwald's confidence. Cutting his way through the soldiers, Macbeth made directly for Macdonwald. Using his sword, he then cut Macdonwald open from the "nave to th'chops" (from his stomach to his jaw) before removing his head and displaying it on the castle walls.
Macbeth is, therefore, the hero of the battle, universally recognized and praised for his bravery and fighting ability.
In act1 sc.2, a bleeding sergeant reports to king Duncan and others how Duncan's brave general defeated and killed the 'merciless Macdonwald' of the Western Isles in battle. Macdonwald assisted by the 'kerns and gallowglasses' was fighting with all his 'villainies of nature' until 'brave Macbeth' appeared on the scene like 'Valour's minion'. Disdaining Fortune which so long favoured the rebel, Macbeth made his passage to face Macdonwald, and instantly put him to death by cutting the villain into pieces from ' the nave to the chaps', and then by exhibiting his severed head on the battlements.
The soldier further reports that the Norwegian king with his arms and men started 'a fresh assault', and again Macbeth along with Banquo fought back with exemplary vengeance 'as cannons overcharg'd with double cracks', bathing themselves in the blood of the enemy soldiers.
Ross enters to complete the battle account. He reports that Macbeth--'that Bellona's bridegroom'--clad in armour and proof against sword/spear, confronted the 'most disloyal traitor', the Thane of Cawdor, to earn victory for Scotland.
Why is Macbeth brave, respected, strong willed and loyal?