The freezing and penetration of molten core fuel and structural materials penetrating into flow channels are important thermal-hydraulics phenomena to safety assessment of postulated core disruptive accidents in liquid metal reactors. The main objective of this study is to investigate fundamental characteristics of freezing and penetration behavior involved in melt and solid mixture flowing on-to structure material. In our study, solid copper particles mixed with molten wood's metal (melting point 78.8 °C) was used as a simulant melt, while stainless steel and brass were used as freezing structures. A series of fundamental experiments was performed to study the effects of solid particles on the freezing and penetration behavior under the various thermal conditions of molten metal and varying solid particle volume fraction and structure metal. The melt flow and distribution were observed using a digital video camera. The melt penetration length on the structure and proportion of adhered frozen metal on to structure surfaces were measured in the present series of experiments. The results indicate that penetration length becomes shorter with increasing solid particles volume fraction in melt. The present results will be utilized to build a relevant database for verification of fast reactor safety analysis codes.