If it is opening maximized, it will fill the full screen within the Access
window. If the form isn't large enough to fill all of that area, you're
correct, it will fit itself into the top, left of its maximized window and
leave the rest of the area blank. The problem is that the form is the entire
maximized window but you only have enough controls and form sections to fill
the portion you mention. It would be possible to get the form to expand its
"background" to fill the full window, but that would still leave a lot of
blank area, it would just be form background now instead of the empty area
you have now. Another option is the scale all controls on the form to get
larger as you maximize the form so that they continue to fill the same
percentage of the form area. This can get complicated.

If you want to run the form maximized in the Access window, but don't need
all the space that that offers, you may want to reduce the size of the
Access window itself. The form will only maximize within the available space
in the Access window. As you move to larger and higher resolution monitors,
this will become more of a problem. I run a high resolution monitor and
absolutely hate when some programmer thinks I need to run everything
maximized. I don't and won't, so don't maximize it for me. All that does is
make me click the restore button to undo what you did. I run the high
resolution so that I can have multiple windows open without them
overlapping, don't steal the screen from me.