Taking into account the plethora of Remote and Virtual Labs (RVLs) that are currently available online, a key problem has emerged from the need of science teachers to be able to find and select them for their lesson plans, in an efficient and effective way. The most common way to facilitate this process using web technologies is to (a) characterize RVLs with appropriately selected educational metadata and (b) to build a web repository that collects the metadata descriptions of RVLs following a common metadata schema and offers search and retrieve facilities. In our previous works we have proposed: (a) a metadata schema for describing RVLs and (b) a web-based repository that stores RVLs based on the proposed metadata schema. In this work, we present the results of an investigation with 93 European school science teachers that was performed in the framework of a major European Initiative namely, the Go-Lab Project. The aim of the study is to identify which metadata elements are considered important by science teachers when they are searching for RVLs that will support their daily teaching activities within the context of their lesson planning.