Changing lanes
When you change lanes, you must give way to any vehicle in the lane you are moving into. This rule applies even if your lane is ending and you have to cross a lane line.
Don’t take risks when changing lanes. Before you change lanes, you must indicate for long enough to give warning to other road users
You must turn off your indicator after you have changed lanes or merged.
Merging
There are 2 different give way rules for merging.
Merging on roads that have lane markings
1. On roads where there are lanes marked on the road—if your lane comes to an end, you must give way to traffic already in the lane you are moving to. In this example, Vehicle A (white) must give way to Vehicle B (yellow).
Merging on roads that don't have lane markings
2. On roads where there are no lanes marked on the road—when lines of traffic merge, you must give way to any vehicle that is ahead of you. In this example, Vehicle B (yellow) must give way to Vehicle A (white).
Lines of traffic refers to adjacent rows of vehicles that do not have a lane separation line between them.
Video of Merging:
https://youtu.be/GQoJsOpw5bg