what is the command/concept ( if ) equivalnt to set metric-type internal in Cisco
Are You after this one?
set metric-type internalTo set the Multi Exit Discriminator (MED) value on prefixes advertised to external BGP (eBGP) neighbors to match the Interior Gateway Protocol (IGP) metric of the next hop
The JUNOS equivalent is:
set policy-options policy-statement IGP->MED term t1 then metric igp
set protocols bgp group ebgp export IGP->MED
Also, if You are exporting IGP prefixes into BGP, the MED == IGP cost will be set automatically without any policy.