Expressing feelings in art for me is quite different from
>>2's way. o3o
First of all, I do three types of "art": doodle/comics, realism drawn from references, and surreal. The first two have absolutley no feeling. I might be feeling something while working on them but I almost always don't give enough shit to show those feelings in the pieces. Or with realism, I try to convey the feeling that was already in the photograph(s) from which I am drawing.
Anywayz if any of my art ever have feeling, you would see it in my surreal crap. When I do surreal things I try to show them how I feel and/or think about something by making the viewer feel a certain way, a way that will help them understand the piece. One of my latest pieces is of a girl that is trying to pull the viewer through a mirror (the canvas itself), so I made her have a messed up face and hold her hands out. There are hands in the background. In my opinion it makes the viewer feel scared or something, as it gives off an oppressive creepystalkerish type of feeling, just like I wanted.
There are simple ways to make people feel certain things when it comes to art. Lines, corners, whatever are usually seen as edgy, sharp, intense and aggressive. Circles and curves make things seem soft and flowy. Minute detail/zoomed out views helps the viewer feel small. There are also colors, like red makes people anxious and blue is calming. You can use symbolism in your art, like guns, blood, darkness to make the viewer feel scared or whatever.