Act I, Sc 2 is one of the 'introductory' scenes of this play. In it Shakespeare not shows us King Duncan and some of his nobles and courtiers, in the battle camp, receiving glad tidings of Macbeth and Banquo's victory against the Norwegian forces and the traitorous Thane of Cawdor (a title which is additionally granted to Macbeth as a reward hitherto by a grateful King Duncan); and, in addition, it goes on to build up upon th premise and ominous air of the first/opening scene.
It is a brief and active scene, all hustle and bustle, and Shakespeare very effectively creates an atmosphere of tension and excitement by various devices: (a) its very brevity and hustle-bustle; a battle is going on and reports of fighting are coming in to headquarters, and the movement is as good as any contemporary 'action movie'; (b) apart from the action/movement the words and tones are clipped and short, spoken in a flurry, and in an atmosphere of tense expectation and we can pick up the palpable undercurrent of stress faced by Duncan and his close aides as well as their sudden joyous outburst at hearing of Maceth;s victory; and (c) finally, Shakespeare, being a consumate master of stagecraft also creates an additional element of suspense in the waiting, placing this scene between the previous one (the mysterious actions and omens of the hags) and the forthcoming one (the hags's meeting with the victorious Macbeth and banquo and their predictions, which also leave us on edge and wondering what is coming next)-- and it is worth noting that all these scenes are short and crisp altogether, and keep the 'flow' of the play moving forward.
In Macbeth the atmosphere of suspense and a brooding evil is created - as pointed bout by Bradley - by three elements 1)darkness, broken by 2) flicker of light (torch, candle etc.) and 3) the colour of blood. Act I, Sc i - by introducing the bloody sergeant - creates the atmosphere; and it is made poignant by the reports of treachery and its consequent defeat, anticipating the betrayal and the tragic fall of Macbeth.