How do I keep the player with rigidbody from going through the wall

My problem is that when the player hits a wall, it ignores it as if it is not an object. both objects have a collider and the player has a rigidbody. This is my script

c#

using UnityEngine; using System.Collections;

public class Game : MonoBehaviour {

 public float speed = 0.3f;
 public Rigidbody rb;
 public GameObject floor;

 // Use this for initialization
 void Start () {
 
     rb = GetComponent<Rigidbody>();
 }
 
 // Update is called once per frame
 void Update () {

     if (Input.GetKey (KeyCode.D)) {

         rb.MovePosition(transform.position + transform.forward * speed);

     } else if (Input.GetKey (KeyCode.A)) {

         rb.MovePosition(transform.position - transform.forward * speed);
     }

     if (Input.GetKey (KeyCode.Space)) {

         Destroy (floor);

     }
 
 }

}