Why does a network host need to broadcast an ARP request?

A host on a network needs to broadcast an ARP request to advertise its Mac address. The networking world is very chatty in nature and when a new network host is available it immediately broadcasts its Mac address as with a ARP message.

Also when a particular network host needs to send a data packet to another network host available in the same LAN whose Mac address is unknown, the first network host sends out a ARP message requesting for the destination network hosts MAC address.