METIS is developing a 5G system concept that meets the requirements of the beyond-2020 connected information society and supports new usage scenarios. To meet the objectives METIS uses Horizontal Topics (HT) that addresses a key new challenge, identifies necessary new functionalities and proposes HT-specific concepts. This paper presents an initial view of the HT-specific concepts for each of the METIS HTs: Direct Device-to-Device Communication, Massive Machine Communication, Moving Networks, Ultra-Dense Networks, and Ultra-Reliable Communication. It also describes how the HT-specific concepts will be integrated into one overall METIS 5G concept.