During his visit, he tweeted that the United States is committed to close consultations with Israel concerning "threats posed by Iran" and Israeli security.
Austin is the first member of Biden's Cabinet to visit Israel since the United States began indirect negotiations last week to rejoin the 2015 Iran nuclear deal.
After their meeting Monday, Netanyahu and Austin gave a joint press briefing during which Netanyahu warned that Iran is keeping up efforts to produce nuclear weapons.
"We're not just allies, we're family. We call that 'mishpacha,'" Netanyahu said. "There is so much truth in that statement that our peoples instinctively understand."
Netanyahu added that there's no threat in the Middle East more dangerous or more pressing than that posed by a "fanatical regime in Iran."
Austin said the United States' strong ties to Israel are "central to regional security in the Middle East" and that he's lobbied for a meeting with Israeli leaders in the early days of the Biden administration.
Israel opposes the Iran nuclear deal and supported the U.S. withdrawal under former President Donald Trump. Biden has said he plans to rejoin the accord, which offers sanctions relief in exchange for limiting Tehran's nuclear activities to the laboratory.
Netanyahu warned last week that Israel will not be bound by any deal world powers make with Iran if it leads to Tehran securing nuclear weapons.
Earlier Monday, Iranian foreign minister Javad Zarif accused Israel of being responsible for causing a blackout Sunday at the Natanz nuclear facility in central Iran and vowed that Tehran will take retaliatory measures.
Iranian officials said an electrical circuit issue caused the power outage. Ali Akbar Salehi, head of Iran's Atomic Energy Organization, called it an act of "nuclear terrorism."
After leaving Israel, Lloyd is scheduled to travel to Germany and then Belgium for meetings with NATO Secretary General Jens Stoltenberg. His trip ends with a visit in Britain later this week.