Holly, from what Iāve gathered Messianic Judaism comes in a couple of varieties. There are, first, Jews who have come to accept Christ and in doing so have embraced a more Evangelical Protestant theology; second, there are some Evangelical Christians who try to incorporate Jewish practices (Sabbath worship and other Jewish holidays) into their lives as Christians. These latter often denigrate and dismiss the teachings of St. Paul because they see him as anti-Jewish; they also tend to be quite anti-Catholic. I think you can see the problems with both versions.
FYI, here is website for the Association of Hebrew Catholics:
Like FCEGM said, there are several different ābrandsā of Messianic Judaism. I was considering Messianic Judaism a couple years ago, so I know a bit about their general beliefs. Among other things they believe in immersion-only baptism, that Mary was not perpetually virgin, and, most significantly (for us anyway), that the Mosaic Law is still required. They donāt accept the Deuterocanon. They also refer to Jesus as Yeshua. I want to get my hands on Dr. David Sternās āJewish Bible,ā which is a Messianic Jewish Old and New Testament that uses the original Hebrew names. Mostly because I collect Bible translations like magpies collect shiny objects.
Grace-based Messianics usually call themselves Christians, rather than say they practice Messianic Judasim. Messianic Judaism can mean many things. It can mean they just believe a Messiah is coming and they totally reject Jesus as Messiah.
But if one calls himself a Messianic Christian, you know his Messiah is Jesus Christ.
The main problem with some Messianic Christians(as well as other Christians) is that they mingle the Mosiac Covenant Law with the better New Covenant of Grace.
DISCLAIMER: Catholic Answers has turned over the archive to Catholic-Questions.org and no longer owns, manages, or moderates the forums. For additional apologetics resources please visit www.catholic.com.