If you know the IP address of the Host, but its not within your physical reach but you want to know what is its MAC address, then just follow below mentioned steps.
Make sure you ping that IP at-least once so this can get address into ARP table.
$ ping -c 1 192.168.1.105
PING 192.168.1.105 (192.168.1.105) 56(84) bytes of data.
64 bytes from 192.168.1.105: icmp_seq=1 ttl=128 time=4.68 ms— 192.168.1.105 ping statistics —
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 4.681/4.681/4.681/0.000 ms
Now user arp command to get rest of details of that IP,
$ arp 192.168.1.105
Address HWtype HWaddress Flags Mask Iface
192.168.1.105 ether MACHINE_MAC C wlan0
Here, we can see the 3rd column as MAC address of the machine / device.