Metcalfe was born in Dublin, and has played club cricket for Malahide and Pembroke. Her debut for Ireland came in June 1999, against an England A team, and her One Day International debut came the following month, at the age of 19, when she played three matches at the 1999 European Championship in Denmark. In July 2000, Metcalfe was selected in Ireland's squad for its inaugural Test match, against Pakistan. In Pakistan's first innings, she took 4/26 from twelve overs to help bowl the team out for 53. Several months later, Metcalfe was selected in the squad for the 2000 World Cup in New Zealand, although she would only play two matches at the tournament. One of Ireland's best spinners, Metcalfe was a regular in the national team throughout the remainder of the 2000s, although she did not gain selection for the 2005 World Cup in South Africa. In an ODI against the Netherlands at the 2007 European Championship, she took her only five-wicket haul at that level, 5/18 from 8.3 overs. Her performance set a new record for the best ODI bowling figures by an Irishwoman, although it has since been surpassed. The following year, at the 2008 World Cup Qualifier, Metcalfe took eight wickets at an average of 14.25, behind only Isobel Joyce for Ireland. Metcalfe announced her retirement from international cricket in 2011, concluding her ODI career with figures of 4/27 against Sri Lanka. In 42 ODIs, she took 50 wickets at an average of 25.08, placing her behind only Isobel Joyce and Barbara McDonald in terms of wickets taken for Ireland. In 2015, however, Metcalfe announced that she would again be available for the national team. Her international appearances since her return have all been at Twenty20 International level, and have included a series against Australia and matches at the 2015 World Twenty20 Qualifier. In June 2018, she was named in Ireland's squad for the 2018 ICC Women's World Twenty20 Qualifier tournament. During the tournament match against Uganda, she took her 100th wicket for Ireland. In October 2018, she was named in Ireland's squad for the 2018 ICC Women's World Twenty20. She announced that she will retire from international cricket following the end of the tournament.
