Install bootlaoder on a raw image created using dd tool

Actually, I want to create an image of my Linux ruing computer(bare-metal). For that, I have created a raw image of it using dd. The command I used to create the image is dd if=/dev/xvda bs=1M of=image.img. Now, I want to install bootloader or whatever is required on image.img so that a bootable USB disk can be created using it. Or, the image can be converted into VDI, VMDK or whatever image format is supported by VirtualBox.