Mr Love was also unanimously elected as the Nationals WA leader on Monday after former leader Mia Davies announced her resignation last week.
"We'll be trying to hold this government to account for the failures that we are experiencing right across (WA) in areas such as housing, in crime, in all the health problem," he told reporters, referring to the McGowan Labor government.
Earlier, Ms Mettam was selected to the Liberal Party's new leader after the incumbent leader David Honey pulled out of a vote for the top job on Monday.
"I put myself forward as leader after considerable reflection and consultation with my colleagues as well as the broader community," she said.
Ms Mettam said the Liberal's parliamentary team had not been as effective as it should have been and the party no longer had the broad support it once had.
"We are listening (and) I understand the internal issues in the party have left some of our supporters disillusioned and can't stand by and assume these issues will fix themselves," she said.
Ms Mettam said there would be changes to her parliamentary team and it was clear the party needed a new direction.
"As the new leader of the Liberal Party my focus will be on rebuilding the party and earning the trust we lost."
Mr Honey said he was disappointed to lose the top job and he stood down after discussions with the party room.
He said he would remain the member for Cottesloe.
"I have the greatest respect for Libby and I will be doing everything that I possibly can to support Libby but also support the Liberal Party and make sure that we go forward to the 2025 election with the best chance of winning," he said.
The pair are WA's only Liberal MPs in the lower house after the party was hammered at the 2021 state election.
The Nationals won four seats, and the two parties formed an alliance with Ms Davies as Opposition leader.
Federal Nationals leader David Littleproud welcomed Mr Love to the top job, saying he had the experience and skills for the role.
"I know Mr Love will do a fantastic job and give Western Australia the best possible chance of forming a Coalition Government at the next election," he said.
Mr Love was previously deputy Opposition leader and deputy leader of the Nationals WA and has served as the member for Moore since 2013.
Peter Rundle was elected as deputy leader of the Nationals WA.
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