Can't get an object to look at object.

So I want in my game, my bullet when instantiated to move towards an object. I use this script:

var clone1 : Rigidbody;

clone1 = Instantiate(Bullet, Muzzle1.position, Muzzle1.rotation);

clone1.velocity = clone1.position * Speed * Time.deltaTime;

But i get an error
" No appropriate version of ‘UnityEngine.Transform.LookAt’ for the argument list ‘(UnityEngine.GameObject)’ was found."

Any ideas?

This is the LookAt function:

void LookAt(Transform target);

It wants a Transform as parameter, not a GameObject;