The metal thing is actually part of the back of this thing:
I guess that I could visually extend the frame in my head (when looking at the picture) but i forgot that any other viewer does not have all that information. I did try to take some from further away, but I couldn't really make the dandelion stand out against the huge metal wheel.
Congratulations on the new camera, also! These are really good shots for your first time out with a new, and different camera. As pointed out before there are some easy to fix compositional problems, but VERY GOOD considering it was your first day.
I agree with the first one. I looked at the belt, and then I looked over and thought, "Oh, I'm supposed to be looking at the dandelion."
I like the second and third ones. The subjects aren't really all that unique or intriguing (who cares about a fence post), but you made good, interesting photos out of them despite this (I care about a fence post now). That's always the sign of a good photographer, a person who can make you look at something with different perspective. You seem to have that.
BTW, I know its difficult as an amateur to convey the feelings you have of a situation into the photograph of it, but I totally agree with you about the contrast of the huge metal track and the frail dandelion. If only there was some way to get that across, but I'm sure you'll get it sooner or later. If not here, then somewhere.
2nd shot seems a bit dark. I've always thought it was neat how trees wrap around wires and such, but for some reason I feel like the only reason I know that this is what this picture is of, is just because I've seen it myself. Brightening could fix that, but I wonder if it needed to be less tight on the crop as well... unsure.
Three seemed too dark as well... almost muted. Probably underexposed.