The meaning or message of a directional line in art depends largely on the direction of the line. Direction lines can be used to lead the viewer's eye through an image.
Diagonal lines demand a lot of attention from viewers. They are filled with energy and are considered emotionally active. They also express movement and depth and convey a sense of visual intensity. A very small diagonal line can have a much greater emotional impact on the viewer than larger horizontal or vertical lines.
Horizontal and vertical lines are more passive emotionally and are also static from a spatial point of view. Horizontal lines convey a message of calmness, while vertical lines send a message of strength.