The angle plays an extraordinarily significant role.
The highest penetration depth is achieved at a 90° angle to the workpiece.
When the electrode is placed at an angle, the metal tends to flow in the direction of the placed electrode. I.e. the metal (e.g. fed wire) follows the direction of movement of the electrode, it is pulled in the direction of the handpiece.
An exception to this rule is silver. (See also item 17)