You can change the field order for the metadata fields in the work item type through the Field Order dialog. Right-click anywhere in the Metadata table and click Field Order in the shortcut menu.
To move a field up or down in the field order, click the field to select it, and then click either the up or down arrow button until the field is in the appropriate position. This is the order in which the fields will appear in the Field dialog when you are creating a work item viewer, but this order can be overridden in the Work Item Viewers dialog After you have added fields to the viewer. See Using the Work Item Viewer Dialog for more information.